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	$189.33	10.513%	$209.2343	$209.23	$209.25	$209.20
Purchase #2	$180.72	6.181%	$191.8903	$191.89	$191.90	$191.90
Purchase #3	$109.90	3.385%	$113.6201	$113.62	$113.60	$113.60
Purchase #4	$146.61	7.857%	$158.1291	$158.13	$158.15	$158.10
Purchase #5	$71.44	10.348%	$78.8326	$78.83	$78.85	$78.80
Purchase #6	$105.68	5.131%	$111.1024	$111.10	$111.10	$111.10
Purchase #7	$50.82	5.533%	$53.6319	$53.63	$53.65	$53.60
7 purchase totals =	$854.50		$916.4407	$916.43	$916.50	$916.30