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	$93.66	10.111%	$103.13	$103.13	$103.15	$103.10
Purchase #2	$77.81	10.141%	$85.7007	$85.70	$85.70	$85.70
Purchase #3	$9.75	13.559%	$11.072	$11.07	$11.05	$11.10
Purchase #4	$137.61	10.238%	$151.6985	$151.70	$151.70	$151.70
Purchase #5	$158.25	8.776%	$172.138	$172.14	$172.15	$172.10
Purchase #6	$243.52	5.494%	$256.899	$256.90	$256.90	$256.90
Purchase #7	$118.50	13.391%	$134.3683	$134.37	$134.35	$134.40
7 purchase totals =	$839.10		$915.0065	$915.01	$915.00	$915.00