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	$204.85	10.510%	$226.3797	$226.38	$226.40	$226.40
Purchase #2	$223.46	12.667%	$251.7657	$251.77	$251.75	$251.80
Purchase #3	$222.75	8.329%	$241.3028	$241.30	$241.30	$241.30
Purchase #4	$190.26	4.790%	$199.3735	$199.37	$199.35	$199.40
Purchase #5	$195.56	9.509%	$214.1558	$214.16	$214.15	$214.20
Purchase #6	$200.75	12.310%	$225.4623	$225.46	$225.45	$225.50
Purchase #7	$47.89	11.130%	$53.2202	$53.22	$53.20	$53.20
7 purchase totals =	$1,285.52		$1,411.6600	$1,411.66	$1,411.60	$1,411.80