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	$57.97	7.684%	$62.4244	$62.42	$62.40	$62.40
Purchase #2	$136.88	13.325%	$155.1193	$155.12	$155.10	$155.10
Purchase #3	$69.54	10.175%	$76.6157	$76.62	$76.60	$76.60
Purchase #4	$167.37	3.585%	$173.3702	$173.37	$173.35	$173.40
Purchase #5	$39.70	13.704%	$45.1405	$45.14	$45.15	$45.10
Purchase #6	$109.46	13.298%	$124.016	$124.02	$124.00	$124.00
Purchase #7	$84.47	7.485%	$90.7926	$90.79	$90.80	$90.80
7 purchase totals =	$665.39		$727.4787	$727.48	$727.40	$727.40