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	$203.99	9.545%	$223.4608	$223.46	$223.45	$223.50
Purchase #2	$94.84	5.606%	$100.1567	$100.16	$100.15	$100.20
Purchase #3	$59.27	3.816%	$61.5317	$61.53	$61.55	$61.50
Purchase #4	$230.96	12.806%	$260.5367	$260.54	$260.55	$260.50
Purchase #5	$177.61	10.251%	$195.8168	$195.82	$195.80	$195.80
Purchase #6	$79.95	13.410%	$90.6713	$90.67	$90.65	$90.70
Purchase #7	$20.89	6.261%	$22.1979	$22.20	$22.20	$22.20
7 purchase totals =	$867.51		$954.3719	$954.38	$954.35	$954.40