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	$172.60	11.342%	$192.1763	$192.18	$192.20	$192.20
Purchase #2	$184.60	7.276%	$198.0315	$198.03	$198.05	$198.00
Purchase #3	$66.87	11.164%	$74.3354	$74.34	$74.35	$74.30
Purchase #4	$235.32	8.749%	$255.9081	$255.91	$255.90	$255.90
Purchase #5	$173.93	13.267%	$197.0053	$197.01	$197.00	$197.00
Purchase #6	$146.29	3.790%	$151.8344	$151.83	$151.85	$151.80
Purchase #7	$27.71	13.706%	$31.5079	$31.51	$31.50	$31.50
7 purchase totals =	$1,007.32		$1,100.7989	$1,100.81	$1,100.85	$1,100.70