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	$110.72	5.388%	$116.6856	$116.69	$116.70	$116.70
Purchase #2	$83.42	4.874%	$87.4859	$87.49	$87.50	$87.50
Purchase #3	$152.86	13.665%	$173.7483	$173.75	$173.75	$173.70
Purchase #4	$67.70	12.437%	$76.1198	$76.12	$76.10	$76.10
Purchase #5	$138.33	10.717%	$153.1548	$153.15	$153.15	$153.20
Purchase #6	$203.39	9.379%	$222.4659	$222.47	$222.45	$222.50
Purchase #7	$159.94	11.559%	$178.4275	$178.43	$178.45	$178.40
7 purchase totals =	$916.36		$1,008.0878	$1,008.10	$1,008.10	$1,008.10