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	$102.31	10.808%	$113.3677	$113.37	$113.35	$113.40
Purchase #2	$142.60	9.120%	$155.6051	$155.61	$155.60	$155.60
Purchase #3	$60.88	7.604%	$65.5093	$65.51	$65.50	$65.50
Purchase #4	$149.35	6.204%	$158.6157	$158.62	$158.60	$158.60
Purchase #5	$82.27	9.180%	$89.8224	$89.82	$89.80	$89.80
Purchase #6	$162.39	9.636%	$178.0379	$178.04	$178.05	$178.00
Purchase #7	$137.42	13.214%	$155.5787	$155.58	$155.60	$155.60
7 purchase totals =	$837.22		$916.5368	$916.55	$916.50	$916.50