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	$166.55	13.349%	$188.7828	$188.78	$188.80	$188.80
Purchase #2	$161.68	7.325%	$173.5231	$173.52	$173.50	$173.50
Purchase #3	$48.62	4.614%	$50.8633	$50.86	$50.85	$50.90
Purchase #4	$133.80	8.238%	$144.8224	$144.82	$144.80	$144.80
Purchase #5	$61.79	9.852%	$67.8776	$67.88	$67.90	$67.90
Purchase #6	$59.87	10.582%	$66.2054	$66.21	$66.20	$66.20
Purchase #7	$31.26	4.472%	$32.6579	$32.66	$32.65	$32.70
7 purchase totals =	$663.57		$724.7325	$724.73	$724.70	$724.80