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	$209.48	10.430%	$231.3288	$231.33	$231.35	$231.30
Purchase #2	$99.58	11.806%	$111.3364	$111.34	$111.35	$111.30
Purchase #3	$209.89	10.324%	$231.559	$231.56	$231.55	$231.60
Purchase #4	$209.25	7.147%	$224.2051	$224.21	$224.20	$224.20
Purchase #5	$157.55	13.196%	$178.3403	$178.34	$178.35	$178.30
Purchase #6	$176.48	9.139%	$192.6085	$192.61	$192.60	$192.60
Purchase #7	$74.29	9.680%	$81.4813	$81.48	$81.50	$81.50
7 purchase totals =	$1,136.52		$1,250.8594	$1,250.87	$1,250.90	$1,250.80