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	$172.75	13.175%	$195.5098	$195.51	$195.50	$195.50
Purchase #2	$244.94	12.237%	$274.9133	$274.91	$274.90	$274.90
Purchase #3	$214.91	13.390%	$243.6864	$243.69	$243.70	$243.70
Purchase #4	$19.42	4.364%	$20.2675	$20.27	$20.25	$20.30
Purchase #5	$82.27	9.161%	$89.8068	$89.81	$89.80	$89.80
Purchase #6	$37.66	13.849%	$42.8755	$42.88	$42.90	$42.90
Purchase #7	$83.42	9.627%	$91.4508	$91.45	$91.45	$91.50
7 purchase totals =	$855.37		$958.5101	$958.52	$958.50	$958.60