Work in cents
One of each selected offer creates an 1187 cent base:329 plus 299 plus 559. A confirmed 11.87 credit leaves zero merchandise. An 11.88 credit is one cent too high and is rejected. Integer cents prevent exact full credit from failing through binary decimal rounding. Inputs accept at most two decimal places rather than silently trimming precision.
Charges remain attached
With separately confirmed shipping 4.99,tax 1.25 and other 0, full merchandise credit still leaves 6.24 in entered charges. This is arithmetic on your inputs, not a claim that all three stores impose those amounts. A promotion may affect tax or delivery under specific rules; use the actual final quote.
Unknown is not zero
Blank shipping, tax or other fields withhold the full total. Enter 0 only when that charge is confirmed zero. Negative, over-precision, exponent or over-limit inputs remain unresolved. The merchandise ledger stays visible so a known subtotal need not masquerade as a fully known checkout.
Retain the record
Save product identity, quantity, date and quote. If checkout applies a promotion differently, replace planning inputs with confirmed lines. The calculator processes no payment, sends no cart and stores no personal shopping information. It cannot guarantee code eligibility or create one real transaction across separate merchants.
A decimal boundary you can inspect
Entering0.10for one selected offer and quantity3produces0.30merchandise,not a floating-point residue. An exact0.30credit is valid and0.31is rejected. Entering0.001does not silently become zero;it is invalid precision. These rules matter when a small promotional or refund amount is close to the subtotal,and keep the result auditable without implying that your edited price is a live retail quote.
Sources & scope
Checked November 5, 2026. Manufacturer and retailer references support the specific statements. Dated displayed prices are not final checkout quotes, performance rankings or performance testing. This shopping reference does not replace the exact product label or qualified individual advice. Current received labels and independent food/nutrition/content/commerce review remain pending.
Cheerios selected Target39602815 ↗