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	$53.39	11.205%	$59.3723	$59.37	$59.35	$59.40
Purchase #2	$20.58	10.141%	$22.667	$22.67	$22.65	$22.70
Purchase #3	$29.52	8.763%	$32.1068	$32.11	$32.10	$32.10
Purchase #4	$137.44	3.105%	$141.7075	$141.71	$141.70	$141.70
Purchase #5	$9.71	5.233%	$10.2181	$10.22	$10.20	$10.20
Purchase #6	$10.48	10.862%	$11.6183	$11.62	$11.60	$11.60
Purchase #7	$230.31	12.526%	$259.1586	$259.16	$259.15	$259.20
7 purchase totals =	$491.43		$536.8486	$536.86	$536.75	$536.90