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	$200.96	10.674%	$222.4105	$222.41	$222.40	$222.40
Purchase #2	$100.34	10.828%	$111.2048	$111.20	$111.20	$111.20
Purchase #3	$248.95	3.869%	$258.5819	$258.58	$258.60	$258.60
Purchase #4	$20.64	12.843%	$23.2908	$23.29	$23.30	$23.30
Purchase #5	$97.40	9.192%	$106.353	$106.35	$106.35	$106.40
Purchase #6	$243.37	13.267%	$275.6579	$275.66	$275.65	$275.70
Purchase #7	$219.60	13.855%	$250.0256	$250.03	$250.05	$250.00
7 purchase totals =	$1,131.26		$1,247.5245	$1,247.52	$1,247.55	$1,247.60