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	$61.31	13.762%	$69.7475	$69.75	$69.75	$69.70
Purchase #2	$70.41	8.603%	$76.4674	$76.47	$76.45	$76.50
Purchase #3	$247.75	10.643%	$274.118	$274.12	$274.10	$274.10
Purchase #4	$62.59	8.198%	$67.7211	$67.72	$67.70	$67.70
Purchase #5	$141.42	11.383%	$157.5178	$157.52	$157.50	$157.50
Purchase #6	$104.78	6.565%	$111.6588	$111.66	$111.65	$111.70
Purchase #7	$105.25	12.283%	$118.1779	$118.18	$118.20	$118.20
7 purchase totals =	$793.51		$875.4085	$875.42	$875.35	$875.40