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	$33.38	8.363%	$36.1716	$36.17	$36.15	$36.20
Purchase #2	$17.78	3.218%	$18.3522	$18.35	$18.35	$18.40
Purchase #3	$145.58	13.724%	$165.5594	$165.56	$165.55	$165.60
Purchase #4	$205.90	7.568%	$221.4825	$221.48	$221.50	$221.50
Purchase #5	$139.84	9.770%	$153.5024	$153.50	$153.50	$153.50
Purchase #6	$90.77	5.485%	$95.7487	$95.75	$95.75	$95.70
Purchase #7	$49.27	8.475%	$53.4456	$53.45	$53.45	$53.40
7 purchase totals =	$682.52		$744.2624	$744.26	$744.25	$744.30