Most currencies round to 2 decimal places (cents)
Exception: Japanese Yen (¥) has no decimal subdivision and rounds to whole numbers
$12.345 → $12.35 (5 in thousandths, round up)
$12.344 → $12.34 (4 in thousandths, round down)
$99.999 → $100.00 (9 in thousandths, round up)
$5.001 → $5.00 (1 in thousandths, round down)
Sales tax often results in fractions of cents
$19.99 × 8.25% = $1.649175 → $1.65
Dividing a restaurant bill among friends
$100 ÷ 3 people = $33.333... → $33.33 each
Monthly interest on savings or loans
$1,000 × 0.5% = $5.123 → $5.12
Calculating price per unit or weight
$10 ÷ 3 pounds = $3.3333/lb → $3.33/lb
Percentage discounts creating fractional cents
$29.99 - 15% = $25.4915 → $25.49
Rounding money is an essential skill in finance, accounting, and everyday transactions. Since most physical currencies only go down to cents (1/100 of a dollar), any calculation that produces smaller fractions must be rounded.
Round Up (Favor Business): $12.341 → $12.35 - Business earns slightly more
Round Down (Favor Customer): $12.349 → $12.34 - Customer pays slightly less
Standard Rounding (Fair): Follows the 5 rule - most common in commerce