<h4>Shopping Cart toFixed Crash Fix</h4><ul><li><strong>Fixed:</strong> "grandTotal.toFixed is not a function" — calculateNewSubtotal() passes grandTotal as a string (from .toFixed(2) which returns string "4.00"), then calculateNewGrandTotal() does grandTotal += total which becomes string concatenation instead of addition, then .toFixed(2) fails on the resulting string. Added parseFloat(grandTotal) at the top of calculateNewGrandTotal to ensure it is always a number.</li></ul>