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	$56.89	13.484%	$64.561	$64.56	$64.55	$64.60
Purchase #2	$149.71	5.684%	$158.2195	$158.22	$158.20	$158.20
Purchase #3	$142.32	11.384%	$158.5217	$158.52	$158.50	$158.50
Purchase #4	$72.98	5.820%	$77.2274	$77.23	$77.25	$77.20
Purchase #5	$116.81	6.449%	$124.3431	$124.34	$124.35	$124.30
Purchase #6	$106.48	9.114%	$116.1846	$116.18	$116.20	$116.20
Purchase #7	$54.74	7.123%	$58.6391	$58.64	$58.65	$58.60
7 purchase totals =	$699.93		$757.6964	$757.69	$757.70	$757.60