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	$66.46	13.700%	$75.565	$75.57	$75.55	$75.60
Purchase #2	$70.92	9.733%	$77.8226	$77.82	$77.80	$77.80
Purchase #3	$91.86	4.247%	$95.7613	$95.76	$95.75	$95.80
Purchase #4	$45.32	13.469%	$51.4242	$51.42	$51.40	$51.40
Purchase #5	$124.72	13.622%	$141.7094	$141.71	$141.70	$141.70
Purchase #6	$246.72	11.262%	$274.5056	$274.51	$274.50	$274.50
Purchase #7	$126.51	3.857%	$131.3895	$131.39	$131.40	$131.40
7 purchase totals =	$772.51		$848.1776	$848.18	$848.10	$848.20