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	$151.38	13.841%	$172.3325	$172.33	$172.35	$172.30
Purchase #2	$147.64	5.217%	$155.3424	$155.34	$155.35	$155.30
Purchase #3	$188.94	3.852%	$196.218	$196.22	$196.20	$196.20
Purchase #4	$192.55	3.660%	$199.5973	$199.60	$199.60	$199.60
Purchase #5	$111.62	10.828%	$123.7062	$123.71	$123.70	$123.70
Purchase #6	$18.86	10.534%	$20.8467	$20.85	$20.85	$20.80
Purchase #7	$83.90	5.578%	$88.5799	$88.58	$88.60	$88.60
7 purchase totals =	$894.89		$956.6230	$956.63	$956.65	$956.50