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	$112.57	11.637%	$125.6698	$125.67	$125.65	$125.70
Purchase #2	$68.58	12.525%	$77.1696	$77.17	$77.15	$77.20
Purchase #3	$34.78	11.733%	$38.8607	$38.86	$38.85	$38.90
Purchase #4	$220.76	3.105%	$227.6146	$227.61	$227.60	$227.60
Purchase #5	$164.60	10.286%	$181.5308	$181.53	$181.55	$181.50
Purchase #6	$153.81	3.268%	$158.8365	$158.84	$158.85	$158.80
Purchase #7	$247.62	9.634%	$271.4757	$271.48	$271.50	$271.50
7 purchase totals =	$1,002.72		$1,081.1577	$1,081.16	$1,081.15	$1,081.20