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	$238.49	7.460%	$256.2814	$256.28	$256.30	$256.30
Purchase #2	$81.60	4.671%	$85.4115	$85.41	$85.40	$85.40
Purchase #3	$145.77	4.550%	$152.4025	$152.40	$152.40	$152.40
Purchase #4	$76.75	11.792%	$85.8004	$85.80	$85.80	$85.80
Purchase #5	$204.63	13.130%	$231.4979	$231.50	$231.50	$231.50
Purchase #6	$166.36	9.747%	$182.5751	$182.58	$182.60	$182.60
Purchase #7	$24.43	7.142%	$26.1748	$26.17	$26.15	$26.20
7 purchase totals =	$938.03		$1,020.1436	$1,020.14	$1,020.15	$1,020.20