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	$111.25	12.308%	$124.9427	$124.94	$124.95	$124.90
Purchase #2	$59.68	11.178%	$66.351	$66.35	$66.35	$66.40
Purchase #3	$11.28	12.525%	$12.6928	$12.69	$12.70	$12.70
Purchase #4	$56.50	5.663%	$59.6996	$59.70	$59.70	$59.70
Purchase #5	$54.33	4.639%	$56.8504	$56.85	$56.85	$56.90
Purchase #6	$139.38	13.269%	$157.8743	$157.87	$157.85	$157.90
Purchase #7	$130.84	11.626%	$146.0515	$146.05	$146.05	$146.10
7 purchase totals =	$563.26		$624.4623	$624.45	$624.45	$624.60