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	$95.52	3.801%	$99.1507	$99.15	$99.15	$99.20
Purchase #2	$216.33	10.388%	$238.8024	$238.80	$238.80	$238.80
Purchase #3	$195.63	13.283%	$221.6155	$221.62	$221.60	$221.60
Purchase #4	$189.28	10.605%	$209.3531	$209.35	$209.35	$209.40
Purchase #5	$144.59	9.626%	$158.5082	$158.51	$158.50	$158.50
Purchase #6	$216.40	13.539%	$245.6984	$245.70	$245.70	$245.70
Purchase #7	$167.41	13.143%	$189.4127	$189.41	$189.40	$189.40
7 purchase totals =	$1,225.16		$1,362.5410	$1,362.54	$1,362.50	$1,362.60