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	$12.52	8.672%	$13.6057	$13.61	$13.60	$13.60
Purchase #2	$147.43	9.657%	$161.6673	$161.67	$161.65	$161.70
Purchase #3	$177.27	12.712%	$199.8046	$199.80	$199.80	$199.80
Purchase #4	$238.75	3.660%	$247.4883	$247.49	$247.50	$247.50
Purchase #5	$155.89	10.369%	$172.0542	$172.05	$172.05	$172.10
Purchase #6	$124.92	6.109%	$132.5514	$132.55	$132.55	$132.60
Purchase #7	$237.85	13.148%	$269.1225	$269.12	$269.10	$269.10
7 purchase totals =	$1,094.63		$1,196.2940	$1,196.29	$1,196.25	$1,196.40