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	$34.53	7.820%	$37.2302	$37.23	$37.25	$37.20
Purchase #2	$20.92	8.289%	$22.6541	$22.65	$22.65	$22.70
Purchase #3	$28.83	5.193%	$30.3271	$30.33	$30.35	$30.30
Purchase #4	$78.71	13.723%	$89.5114	$89.51	$89.50	$89.50
Purchase #5	$43.39	3.861%	$45.0653	$45.07	$45.05	$45.10
Purchase #6	$238.49	9.513%	$261.1776	$261.18	$261.20	$261.20
Purchase #7	$126.28	4.874%	$132.4349	$132.43	$132.45	$132.40
7 purchase totals =	$571.15		$618.4006	$618.40	$618.45	$618.40