The Trailing Zero Rule: Always write two decimal places in your final answer, even if the second digit is zero. For example, write 5.40 dollars instead of 5.4 dollars.
Sanity Checks: After calculating a total, perform a quick estimation. If you buy 10 items at 1.95 dollars each, your answer should be slightly less than 20 dollars. If it is 195 dollars, you likely misplaced a decimal.
Unit Consistency: Ensure all values are in the same unit (either all dollars or all cents) before performing addition or subtraction.
Premature Rounding: Rounding a price like 1.579 to 1.58 before multiplying by a large quantity will result in an inaccurate total.
Decimal Misalignment: Failing to line up decimal points during manual subtraction (especially when 'borrowing' across zeros) is a frequent source of error in change calculations.
Currency Symbol Errors: Forgetting to include the correct currency symbol (USD, GBP, etc.) or using the wrong symbol for the context of the question.
