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	$154.53	4.733%	$161.8439	$161.84	$161.85	$161.80
Purchase #2	$43.86	3.756%	$45.5074	$45.51	$45.50	$45.50
Purchase #3	$33.29	9.686%	$36.5145	$36.51	$36.50	$36.50
Purchase #4	$13.54	3.676%	$14.0377	$14.04	$14.05	$14.00
Purchase #5	$82.34	10.739%	$91.1825	$91.18	$91.20	$91.20
Purchase #6	$187.89	9.338%	$205.4352	$205.44	$205.45	$205.40
Purchase #7	$47.45	13.531%	$53.8705	$53.87	$53.85	$53.90
7 purchase totals =	$562.90		$608.3917	$608.39	$608.40	$608.30