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	$33.34	6.240%	$35.4204	$35.42	$35.40	$35.40
Purchase #2	$125.52	13.763%	$142.7953	$142.80	$142.80	$142.80
Purchase #3	$144.53	5.660%	$152.7104	$152.71	$152.70	$152.70
Purchase #4	$138.87	9.240%	$151.7016	$151.70	$151.70	$151.70
Purchase #5	$142.71	13.152%	$161.4792	$161.48	$161.50	$161.50
Purchase #6	$111.77	10.664%	$123.6892	$123.69	$123.70	$123.70
Purchase #7	$176.51	6.495%	$187.9743	$187.97	$187.95	$188.00
7 purchase totals =	$873.25		$955.7704	$955.77	$955.75	$955.80