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	$173.53	8.178%	$187.7213	$187.72	$187.70	$187.70
Purchase #2	$37.82	8.256%	$40.9424	$40.94	$40.95	$40.90
Purchase #3	$143.80	10.461%	$158.8429	$158.84	$158.85	$158.80
Purchase #4	$54.54	11.138%	$60.6147	$60.61	$60.60	$60.60
Purchase #5	$203.54	7.273%	$218.3435	$218.34	$218.35	$218.30
Purchase #6	$81.56	7.239%	$87.4641	$87.46	$87.45	$87.50
Purchase #7	$158.37	13.539%	$179.8117	$179.81	$179.80	$179.80
7 purchase totals =	$853.16		$933.7406	$933.72	$933.70	$933.60