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	$83.76	3.726%	$86.8809	$86.88	$86.90	$86.90
Purchase #2	$212.65	6.501%	$226.4744	$226.47	$226.45	$226.50
Purchase #3	$188.32	6.431%	$200.4309	$200.43	$200.45	$200.40
Purchase #4	$102.28	9.152%	$111.6407	$111.64	$111.65	$111.60
Purchase #5	$151.58	6.168%	$160.9295	$160.93	$160.95	$160.90
Purchase #6	$164.61	5.665%	$173.9352	$173.94	$173.95	$173.90
Purchase #7	$11.26	3.549%	$11.6596	$11.66	$11.65	$11.70
7 purchase totals =	$914.46		$971.9512	$971.95	$972.00	$971.90