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	$59.89	13.261%	$67.832	$67.83	$67.85	$67.80
Purchase #2	$124.25	5.323%	$130.8638	$130.86	$130.85	$130.90
Purchase #3	$130.39	10.817%	$144.4943	$144.49	$144.50	$144.50
Purchase #4	$106.90	4.522%	$111.734	$111.73	$111.75	$111.70
Purchase #5	$154.27	12.286%	$173.2236	$173.22	$173.20	$173.20
Purchase #6	$15.56	4.107%	$16.199	$16.20	$16.20	$16.20
Purchase #7	$152.75	4.624%	$159.8132	$159.81	$159.80	$159.80
7 purchase totals =	$744.01		$804.1599	$804.14	$804.15	$804.10