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	$50.85	6.647%	$54.23	$54.23	$54.25	$54.20
Purchase #2	$152.93	12.500%	$172.0463	$172.05	$172.05	$172.00
Purchase #3	$245.31	13.612%	$278.7016	$278.70	$278.70	$278.70
Purchase #4	$171.57	12.182%	$192.4707	$192.47	$192.45	$192.50
Purchase #5	$85.66	7.716%	$92.2695	$92.27	$92.25	$92.30
Purchase #6	$179.36	10.492%	$198.1785	$198.18	$198.20	$198.20
Purchase #7	$147.61	7.389%	$158.5169	$158.52	$158.50	$158.50
7 purchase totals =	$1,033.29		$1,146.4135	$1,146.42	$1,146.40	$1,146.40