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	$223.39	11.105%	$248.1975	$248.20	$248.20	$248.20
Purchase #2	$57.71	13.301%	$65.386	$65.39	$65.40	$65.40
Purchase #3	$247.67	11.238%	$275.5032	$275.50	$275.50	$275.50
Purchase #4	$208.51	6.649%	$222.3738	$222.37	$222.35	$222.40
Purchase #5	$52.44	11.207%	$58.317	$58.32	$58.30	$58.30
Purchase #6	$65.44	13.518%	$74.2862	$74.29	$74.30	$74.30
Purchase #7	$61.45	3.281%	$63.4662	$63.47	$63.45	$63.50
7 purchase totals =	$916.61		$1,007.5299	$1,007.54	$1,007.50	$1,007.60