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	$11.68	3.441%	$12.0819	$12.08	$12.10	$12.10
Purchase #2	$76.85	6.205%	$81.6185	$81.62	$81.60	$81.60
Purchase #3	$214.74	4.231%	$223.8256	$223.83	$223.85	$223.80
Purchase #4	$195.95	11.102%	$217.7044	$217.70	$217.70	$217.70
Purchase #5	$203.53	13.746%	$231.5072	$231.51	$231.50	$231.50
Purchase #6	$65.57	10.571%	$72.5014	$72.50	$72.50	$72.50
Purchase #7	$201.61	10.341%	$222.4585	$222.46	$222.45	$222.50
7 purchase totals =	$969.93		$1,061.6975	$1,061.70	$1,061.70	$1,061.70