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	$72.39	12.530%	$81.4605	$81.46	$81.45	$81.50
Purchase #2	$45.89	7.585%	$49.3708	$49.37	$49.35	$49.40
Purchase #3	$77.51	11.605%	$86.505	$86.51	$86.50	$86.50
Purchase #4	$30.45	7.135%	$32.6226	$32.62	$32.60	$32.60
Purchase #5	$154.29	4.151%	$160.6946	$160.69	$160.70	$160.70
Purchase #6	$61.59	9.467%	$67.4207	$67.42	$67.40	$67.40
Purchase #7	$136.31	7.486%	$146.5142	$146.51	$146.50	$146.50
7 purchase totals =	$578.43		$624.5884	$624.58	$624.50	$624.60