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	$92.82	11.730%	$103.7078	$103.71	$103.70	$103.70
Purchase #2	$183.25	9.457%	$200.58	$200.58	$200.60	$200.60
Purchase #3	$6.43	9.461%	$7.0383	$7.04	$7.05	$7.00
Purchase #4	$37.45	9.262%	$40.9186	$40.92	$40.90	$40.90
Purchase #5	$55.46	5.532%	$58.528	$58.53	$58.55	$58.50
Purchase #6	$236.59	8.519%	$256.7451	$256.75	$256.75	$256.70
Purchase #7	$25.38	13.290%	$28.753	$28.75	$28.75	$28.80
7 purchase totals =	$637.38		$696.2708	$696.28	$696.30	$696.20