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	$203.75	5.317%	$214.5834	$214.58	$214.60	$214.60
Purchase #2	$133.57	10.593%	$147.7191	$147.72	$147.70	$147.70
Purchase #3	$102.48	8.725%	$111.4214	$111.42	$111.40	$111.40
Purchase #4	$177.51	10.743%	$196.5799	$196.58	$196.60	$196.60
Purchase #5	$147.35	6.306%	$156.6419	$156.64	$156.65	$156.60
Purchase #6	$149.66	13.388%	$169.6965	$169.70	$169.70	$169.70
Purchase #7	$184.78	10.165%	$203.5629	$203.56	$203.55	$203.60
7 purchase totals =	$1,099.10		$1,200.2051	$1,200.20	$1,200.20	$1,200.20