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	$85.72	13.388%	$97.1962	$97.20	$97.20	$97.20
Purchase #2	$65.77	8.725%	$71.5084	$71.51	$71.50	$71.50
Purchase #3	$231.99	10.491%	$256.3281	$256.33	$256.35	$256.30
Purchase #4	$146.91	13.339%	$166.5063	$166.51	$166.50	$166.50
Purchase #5	$127.45	5.240%	$134.1284	$134.13	$134.15	$134.10
Purchase #6	$36.79	5.401%	$38.777	$38.78	$38.80	$38.80
Purchase #7	$194.72	13.547%	$221.0987	$221.10	$221.10	$221.10
7 purchase totals =	$889.35		$985.5431	$985.56	$985.60	$985.50