Why POS receipts can show GST totals a few paise apart depending on rounding order

Point-of-sale systems can apply the correct GST rate yet still produce tax totals that differ by a few paise from what cashiers or customers expect. The gap often stems from decimal precision, rounding rules, discounts, and whether rounding happens per item or on the invoice total. Such differences matter for retailers, restaurants, and multi-outlet businesses that must reconcile accounts. Since rounding is not distributive, calculating tax per line and then rounding can yield a different total than calculating on the combined taxable amount. The author argues that POS software should follow a consistent, clearly defined tax policy rather than simply rounding every figure to two decimal places.