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	$107.54	3.819%	$111.647	$111.65	$111.65	$111.60
Purchase #2	$127.42	13.303%	$144.3707	$144.37	$144.35	$144.40
Purchase #3	$202.72	8.582%	$220.1174	$220.12	$220.10	$220.10
Purchase #4	$9.56	12.342%	$10.7399	$10.74	$10.75	$10.70
Purchase #5	$15.98	11.299%	$17.7856	$17.79	$17.80	$17.80
Purchase #6	$131.52	4.130%	$136.9518	$136.95	$136.95	$137.00
Purchase #7	$95.29	10.661%	$105.4489	$105.45	$105.45	$105.40
7 purchase totals =	$690.03		$747.0613	$747.07	$747.05	$747.00