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	$52.70	3.634%	$54.6151	$54.62	$54.60	$54.60
Purchase #2	$214.81	7.487%	$230.8928	$230.89	$230.90	$230.90
Purchase #3	$36.56	5.136%	$38.4377	$38.44	$38.45	$38.40
Purchase #4	$232.67	9.381%	$254.4968	$254.50	$254.50	$254.50
Purchase #5	$27.95	11.113%	$31.0561	$31.06	$31.05	$31.10
Purchase #6	$40.34	7.442%	$43.3421	$43.34	$43.35	$43.30
Purchase #7	$184.70	3.153%	$190.5236	$190.52	$190.50	$190.50
7 purchase totals =	$789.73		$843.3642	$843.37	$843.35	$843.30