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	$33.69	11.664%	$37.6196	$37.62	$37.60	$37.60
Purchase #2	$68.35	6.559%	$72.8331	$72.83	$72.85	$72.80
Purchase #3	$191.77	7.510%	$206.1719	$206.17	$206.15	$206.20
Purchase #4	$152.48	13.385%	$172.8894	$172.89	$172.90	$172.90
Purchase #5	$75.26	7.640%	$81.0099	$81.01	$81.00	$81.00
Purchase #6	$169.87	11.763%	$189.8518	$189.85	$189.85	$189.90
Purchase #7	$159.93	8.252%	$173.1274	$173.13	$173.15	$173.10
7 purchase totals =	$851.35		$933.5031	$933.50	$933.50	$933.50