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	$57.31	3.733%	$59.4494	$59.45	$59.45	$59.40
Purchase #2	$21.68	5.580%	$22.8897	$22.89	$22.90	$22.90
Purchase #3	$62.56	8.592%	$67.9352	$67.94	$67.95	$67.90
Purchase #4	$143.54	5.735%	$151.772	$151.77	$151.75	$151.80
Purchase #5	$195.31	13.601%	$221.8741	$221.87	$221.85	$221.90
Purchase #6	$178.52	6.717%	$190.5112	$190.51	$190.50	$190.50
Purchase #7	$170.40	7.522%	$183.2175	$183.22	$183.20	$183.20
7 purchase totals =	$829.32		$897.6491	$897.65	$897.60	$897.60