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	$200.75	10.675%	$222.1801	$222.18	$222.20	$222.20
Purchase #2	$39.84	5.226%	$41.922	$41.92	$41.90	$41.90
Purchase #3	$73.99	12.307%	$83.0959	$83.10	$83.10	$83.10
Purchase #4	$102.36	8.508%	$111.0688	$111.07	$111.05	$111.10
Purchase #5	$149.40	5.845%	$158.1324	$158.13	$158.15	$158.10
Purchase #6	$84.83	8.577%	$92.1059	$92.11	$92.10	$92.10
Purchase #7	$207.71	7.549%	$223.39	$223.39	$223.40	$223.40
7 purchase totals =	$858.88		$931.8951	$931.90	$931.90	$931.90