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	$171.82	11.115%	$190.9178	$190.92	$190.90	$190.90
Purchase #2	$43.43	5.434%	$45.79	$45.79	$45.80	$45.80
Purchase #3	$59.27	5.577%	$62.5755	$62.58	$62.60	$62.60
Purchase #4	$224.75	13.255%	$254.5406	$254.54	$254.55	$254.50
Purchase #5	$55.51	5.439%	$58.5292	$58.53	$58.55	$58.50
Purchase #6	$247.81	5.218%	$260.7407	$260.74	$260.75	$260.70
Purchase #7	$192.58	11.210%	$214.1682	$214.17	$214.15	$214.20
7 purchase totals =	$995.17		$1,087.2620	$1,087.27	$1,087.30	$1,087.20