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	$122.39	3.690%	$126.9062	$126.91	$126.90	$126.90
Purchase #2	$140.59	7.563%	$151.2228	$151.22	$151.20	$151.20
Purchase #3	$98.42	13.499%	$111.7057	$111.71	$111.70	$111.70
Purchase #4	$246.61	3.717%	$255.7765	$255.78	$255.80	$255.80
Purchase #5	$84.43	9.588%	$92.5251	$92.53	$92.55	$92.50
Purchase #6	$48.96	11.731%	$54.7035	$54.70	$54.70	$54.70
Purchase #7	$248.38	11.106%	$275.9651	$275.97	$275.95	$276.00
7 purchase totals =	$989.78		$1,068.8049	$1,068.82	$1,068.80	$1,068.80