A price-and-tax calculation is trustworthy only when its order and authority are explicit. DiscountCalc offers one mathematical scenario: apply the percentage discount, then apply the tax rate supplied by the user to the discounted subtotal. It does not claim that this order or rate is legally correct for any location or item.
Discount first, supplied tax second
For $100 with 20% off, the discounted subtotal is exactly $80. If the user then enters 8.25%, tax is 80 × 8.25/100 = $6.60 and the displayed total is $86.60. The calculation says nothing about whether the tax base or rate matches a real receipt; both remain user assumptions.
Keep exact values until display
Decimal text becomes an exact fraction, so 8.25% is 825/10000 rather than a nearby binary floating-point value. Intermediate discounts and tax remain rational. DiscountCalc rounds monetary displays to two decimals only at the end of each visible result and never feeds that rounded text into another calculation stage.
A receipt may round and allocate differently
A merchant may allocate a basket coupon across items, round each line, exclude products, charge fees, or use rules defined by law and payment systems. Those details can shift the final cents even when the broad formula looks similar. Treat the calculator as a transparent scenario, then use the actual terms and receipt as authority.