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	$118.28	3.636%	$122.5807	$122.58	$122.60	$122.60
Purchase #2	$161.30	10.546%	$178.3107	$178.31	$178.30	$178.30
Purchase #3	$14.72	5.753%	$15.5668	$15.57	$15.55	$15.60
Purchase #4	$119.92	13.785%	$136.451	$136.45	$136.45	$136.50
Purchase #5	$52.30	13.823%	$59.5294	$59.53	$59.55	$59.50
Purchase #6	$34.29	8.792%	$37.3048	$37.30	$37.30	$37.30
Purchase #7	$133.95	11.344%	$149.1453	$149.15	$149.15	$149.10
7 purchase totals =	$634.76		$698.8887	$698.89	$698.90	$698.90