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	$136.45	7.447%	$146.6114	$146.61	$146.60	$146.60
Purchase #2	$118.58	9.692%	$130.0728	$130.07	$130.05	$130.10
Purchase #3	$40.40	7.868%	$43.5787	$43.58	$43.60	$43.60
Purchase #4	$34.59	8.313%	$37.4655	$37.47	$37.45	$37.50
Purchase #5	$199.85	10.358%	$220.5505	$220.55	$220.55	$220.60
Purchase #6	$31.88	5.448%	$33.6168	$33.62	$33.60	$33.60
Purchase #7	$138.71	12.188%	$155.616	$155.62	$155.60	$155.60
7 purchase totals =	$700.46		$767.5117	$767.52	$767.45	$767.60