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	$59.73	11.407%	$66.5434	$66.54	$66.55	$66.50
Purchase #2	$12.46	10.105%	$13.7191	$13.72	$13.70	$13.70
Purchase #3	$96.50	5.240%	$101.5566	$101.56	$101.55	$101.60
Purchase #4	$84.68	4.807%	$88.7506	$88.75	$88.75	$88.80
Purchase #5	$120.37	13.672%	$136.827	$136.83	$136.85	$136.80
Purchase #6	$32.58	13.407%	$36.948	$36.95	$36.95	$36.90
Purchase #7	$140.71	12.461%	$158.2439	$158.24	$158.25	$158.20
7 purchase totals =	$547.03		$602.5886	$602.59	$602.60	$602.50