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	$95.56	10.110%	$105.2211	$105.22	$105.20	$105.20
Purchase #2	$100.60	5.599%	$106.2326	$106.23	$106.25	$106.20
Purchase #3	$70.77	4.726%	$74.1146	$74.11	$74.10	$74.10
Purchase #4	$74.61	5.455%	$78.68	$78.68	$78.70	$78.70
Purchase #5	$93.48	10.808%	$103.5833	$103.58	$103.60	$103.60
Purchase #6	$50.71	5.465%	$53.4813	$53.48	$53.50	$53.50
Purchase #7	$151.75	9.586%	$166.2968	$166.30	$166.30	$166.30
7 purchase totals =	$637.48		$687.6097	$687.60	$687.65	$687.60