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	$232.32	10.442%	$256.5789	$256.58	$256.60	$256.60
Purchase #2	$106.97	7.173%	$114.643	$114.64	$114.65	$114.60
Purchase #3	$27.55	7.157%	$29.5218	$29.52	$29.50	$29.50
Purchase #4	$88.96	13.385%	$100.8673	$100.87	$100.85	$100.90
Purchase #5	$137.95	7.602%	$148.437	$148.44	$148.45	$148.40
Purchase #6	$57.69	7.378%	$61.9464	$61.95	$61.95	$61.90
Purchase #7	$157.27	9.727%	$172.5677	$172.57	$172.55	$172.60
7 purchase totals =	$808.71		$884.5621	$884.57	$884.55	$884.50