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	$106.86	9.105%	$116.5896	$116.59	$116.60	$116.60
Purchase #2	$35.77	5.509%	$37.7406	$37.74	$37.75	$37.70
Purchase #3	$71.50	7.706%	$77.0098	$77.01	$77.00	$77.00
Purchase #4	$59.49	8.624%	$64.6204	$64.62	$64.60	$64.60
Purchase #5	$62.48	8.178%	$67.5896	$67.59	$67.60	$67.60
Purchase #6	$19.58	13.414%	$22.2065	$22.21	$22.20	$22.20
Purchase #7	$43.51	3.480%	$45.0241	$45.02	$45.00	$45.00
7 purchase totals =	$399.19		$430.7806	$430.78	$430.75	$430.70