Sales tax rounds up when the fractional cent is half a cent or more, and rounds down when it is less than half a cent. So does sales tax round up or down in your specific case? Run the multiplication out to at least the third decimal place: if that third digit is 5 or higher, the tax rounds up to the next penny; if it is 4 or lower, it drops. Twenty-four states have written this rule into their tax codes through the Streamlined Sales and Use Tax Agreement, and most other states follow the same math.1Streamlined Sales Tax. Approved Rounding Rules
How the Half-Cent Rule Actually Works
A tax calculation of $1.234 becomes $1.23. A calculation of $1.235 becomes $1.24. The rule sounds simple, but the decimal place you round from can change the answer.
Take a $10.99 item at a 6.25% tax rate. The raw math gives $0.686875. A register that truncated at two decimals would charge $0.68. A register that carried the calculation to three decimals sees $0.687, spots a third digit greater than 4, and rounds up to $0.69. Across thousands of receipts, that one-penny gap matters, which is why Section 324 of the Streamlined Sales and Use Tax Agreement requires the computation be carried to the third decimal place before rounding.2Streamlined Sales Tax. Streamlined Sales and Use Tax Agreement – Section 324
Some states allow or require calculations carried out to four, five, or even six decimal places before the final rounding step. The result usually lands on the same penny, but the extra precision can matter on high-dollar or high-volume transactions where intermediate rounding compounds.
When the Rounding Happens: Per Item or Per Invoice
The point in the checkout where rounding kicks in can shift the total by a few cents. Under SSUTA Section 324, sellers may choose to round on each line item or on the combined invoice total.3Streamlined Sales Tax. Streamlined Sales and Use Tax Agreement – Section 324
Consider three items at $1.05 each in a 7% tax jurisdiction:
- Item-level rounding: each item generates $0.0735 in tax, which rounds to $0.07. Three items produce $0.21 in total tax.
- Invoice-level rounding: the subtotal is $3.15. Tax on $3.15 at 7% is $0.2205, which rounds to $0.22.
The gap comes from rounding down three times at the item level rather than once on the larger total. Some jurisdictions add a floor: if a merchant rounds at the item level, the total tax still has to equal at least what the invoice-level calculation would have produced.2Streamlined Sales Tax. Streamlined Sales and Use Tax Agreement – Section 324 Most modern point-of-sale systems default to invoice-level rounding.
Combined State, County, and City Rates
Many purchases carry overlapping taxes: a state rate, a county rate, and often a city or special-district rate. The SSUTA lets sellers add the rates together and apply the rounding algorithm once to the combined figure, rather than rounding each layer separately.3Streamlined Sales Tax. Streamlined Sales and Use Tax Agreement – Section 324 Aggregating before rounding produces a more accurate result than rounding each jurisdiction’s share on its own.
A few states require separate calculations for certain tax types, particularly in telecommunications where state and local levies are governed by different statutes. If your business runs across overlapping taxing districts, check with each state’s revenue department to confirm whether rates should be combined before rounding.
States That Use Bracket Tables Instead
A small number of states skip the arithmetic altogether and publish a bracket table. Under a bracket system, the retailer looks up the sale price in a chart and charges the penny amount listed for that range. Because the brackets are set by legislative formula, the result can differ slightly from what standard rounding would produce.
SSUTA member states cannot require bracket-based collection, so bracket tables survive only in certain non-member states.3Streamlined Sales Tax. Streamlined Sales and Use Tax Agreement – Section 324 Several states that historically used them have moved to the standard rounding algorithm. If you are unsure which method applies where you do business, the state department of revenue publishes the current instructions.
Cash Rounding to the Nearest Nickel Is Separate
Some retailers round the final cash total to the nearest nickel, a practice sometimes called Swedish rounding. This is not sales tax rounding. The tax is still calculated using the half-cent rule; only the amount of physical currency the customer hands over gets adjusted.
Under Swedish rounding, totals ending in 1, 2, 6, or 7 cents round down, and totals ending in 3, 4, 8, or 9 cents round up. A handful of states have issued guidance accepting the practice for cash transactions, and a few have considered always rounding down. Credit and debit card payments are not affected, because electronic payments settle to the exact penny.