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	$82.52	3.363%	$85.2951	$85.30	$85.30	$85.30
Purchase #2	$228.74	5.496%	$241.3116	$241.31	$241.30	$241.30
Purchase #3	$195.67	10.381%	$215.9825	$215.98	$216.00	$216.00
Purchase #4	$9.25	13.421%	$10.4914	$10.49	$10.50	$10.50
Purchase #5	$67.52	5.542%	$71.262	$71.26	$71.25	$71.30
Purchase #6	$137.55	4.429%	$143.6421	$143.64	$143.65	$143.60
Purchase #7	$88.57	12.669%	$99.7909	$99.79	$99.80	$99.80
7 purchase totals =	$809.82		$867.7756	$867.77	$867.80	$867.80