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	$202.37	13.786%	$230.2687	$230.27	$230.25	$230.30
Purchase #2	$42.96	13.723%	$48.8554	$48.86	$48.85	$48.90
Purchase #3	$12.35	3.389%	$12.7685	$12.77	$12.75	$12.80
Purchase #4	$59.43	10.685%	$65.7801	$65.78	$65.80	$65.80
Purchase #5	$30.25	6.290%	$32.1527	$32.15	$32.15	$32.20
Purchase #6	$15.35	8.222%	$16.6121	$16.61	$16.60	$16.60
Purchase #7	$155.35	4.659%	$162.5878	$162.59	$162.60	$162.60
7 purchase totals =	$518.06		$569.0253	$569.03	$569.00	$569.20