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	$132.76	10.394%	$146.5591	$146.56	$146.55	$146.60
Purchase #2	$231.27	10.762%	$256.1593	$256.16	$256.15	$256.20
Purchase #3	$91.66	8.324%	$99.2898	$99.29	$99.30	$99.30
Purchase #4	$82.39	9.530%	$90.2418	$90.24	$90.25	$90.20
Purchase #5	$10.86	6.824%	$11.6011	$11.60	$11.60	$11.60
Purchase #6	$80.86	10.723%	$89.5306	$89.53	$89.55	$89.50
Purchase #7	$239.93	3.218%	$247.6509	$247.65	$247.65	$247.70
7 purchase totals =	$869.73		$941.0326	$941.03	$941.05	$941.10