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	$83.88	11.863%	$93.8307	$93.83	$93.85	$93.80
Purchase #2	$90.79	10.831%	$100.6235	$100.62	$100.60	$100.60
Purchase #3	$159.51	8.776%	$173.5086	$173.51	$173.50	$173.50
Purchase #4	$142.61	12.332%	$160.1967	$160.20	$160.20	$160.20
Purchase #5	$20.74	13.688%	$23.5789	$23.58	$23.60	$23.60
Purchase #6	$192.33	3.545%	$199.1481	$199.15	$199.15	$199.10
Purchase #7	$45.28	11.868%	$50.6538	$50.65	$50.65	$50.70
7 purchase totals =	$735.14		$801.5403	$801.54	$801.55	$801.50