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	$177.58	7.505%	$190.9074	$190.91	$190.90	$190.90
Purchase #2	$155.87	8.247%	$168.7246	$168.72	$168.70	$168.70
Purchase #3	$102.41	13.795%	$116.5375	$116.54	$116.55	$116.50
Purchase #4	$159.87	3.281%	$165.1153	$165.12	$165.10	$165.10
Purchase #5	$30.64	8.270%	$33.1739	$33.17	$33.15	$33.20
Purchase #6	$217.48	11.606%	$242.7207	$242.72	$242.70	$242.70
Purchase #7	$31.27	10.358%	$34.5089	$34.51	$34.50	$34.50
7 purchase totals =	$875.12		$951.6883	$951.69	$951.60	$951.60