Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$195.43	11.194%	$217.3064	$217.31	$217.30	$217.30
Purchase #2	$178.96	9.468%	$195.9039	$195.90	$195.90	$195.90
Purchase #3	$131.82	7.185%	$141.2913	$141.29	$141.30	$141.30
Purchase #4	$200.91	10.525%	$222.0558	$222.06	$222.05	$222.10
Purchase #5	$223.69	13.177%	$253.1656	$253.17	$253.15	$253.20
Purchase #6	$37.38	9.729%	$41.0167	$41.02	$41.00	$41.00
Purchase #7	$17.31	8.612%	$18.8007	$18.80	$18.80	$18.80
7 purchase totals =	$985.50		$1,089.5404	$1,089.55	$1,089.50	$1,089.60