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	$33.59	10.492%	$37.1143	$37.11	$37.10	$37.10
Purchase #2	$144.65	4.503%	$151.1636	$151.16	$151.15	$151.20
Purchase #3	$46.55	7.793%	$50.1776	$50.18	$50.20	$50.20
Purchase #4	$218.65	3.463%	$226.2218	$226.22	$226.20	$226.20
Purchase #5	$103.27	8.300%	$111.8414	$111.84	$111.85	$111.80
Purchase #6	$66.36	9.363%	$72.5733	$72.57	$72.55	$72.60
Purchase #7	$190.85	9.558%	$209.0914	$209.09	$209.10	$209.10
7 purchase totals =	$803.92		$858.1834	$858.17	$858.15	$858.20