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	$115.26	13.418%	$130.7256	$130.73	$130.75	$130.70
Purchase #2	$39.57	3.141%	$40.8129	$40.81	$40.80	$40.80
Purchase #3	$61.26	9.198%	$66.8947	$66.89	$66.90	$66.90
Purchase #4	$64.67	3.743%	$67.0906	$67.09	$67.10	$67.10
Purchase #5	$42.53	9.353%	$46.5078	$46.51	$46.50	$46.50
Purchase #6	$239.88	6.545%	$255.5801	$255.58	$255.60	$255.60
Purchase #7	$58.31	4.458%	$60.9095	$60.91	$60.90	$60.90
7 purchase totals =	$621.48		$668.5212	$668.52	$668.55	$668.50