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	$85.41	7.501%	$91.8166	$91.82	$91.80	$91.80
Purchase #2	$28.47	9.268%	$31.1086	$31.11	$31.10	$31.10
Purchase #3	$140.55	4.388%	$146.7173	$146.72	$146.70	$146.70
Purchase #4	$154.53	11.274%	$171.9517	$171.95	$171.95	$172.00
Purchase #5	$133.30	10.389%	$147.1485	$147.15	$147.15	$147.10
Purchase #6	$51.33	9.504%	$56.2084	$56.21	$56.20	$56.20
Purchase #7	$59.83	11.497%	$66.7087	$66.71	$66.70	$66.70
7 purchase totals =	$653.42		$711.6598	$711.67	$711.60	$711.60