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	$68.28	12.857%	$77.0588	$77.06	$77.05	$77.10
Purchase #2	$50.41	8.654%	$54.7725	$54.77	$54.75	$54.80
Purchase #3	$141.98	11.707%	$158.6016	$158.60	$158.60	$158.60
Purchase #4	$161.80	6.595%	$172.4707	$172.47	$172.45	$172.50
Purchase #5	$175.34	8.602%	$190.4227	$190.42	$190.40	$190.40
Purchase #6	$32.76	11.307%	$36.4642	$36.46	$36.45	$36.50
Purchase #7	$193.78	6.230%	$205.8525	$205.85	$205.85	$205.90
7 purchase totals =	$824.35		$895.6430	$895.63	$895.55	$895.80