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	$94.69	9.105%	$103.3115	$103.31	$103.30	$103.30
Purchase #2	$40.61	13.530%	$46.1045	$46.10	$46.10	$46.10
Purchase #3	$57.96	4.792%	$60.7374	$60.74	$60.75	$60.70
Purchase #4	$58.74	5.232%	$61.8133	$61.81	$61.80	$61.80
Purchase #5	$250.39	3.695%	$259.6419	$259.64	$259.65	$259.60
Purchase #6	$58.93	13.536%	$66.9068	$66.91	$66.90	$66.90
Purchase #7	$131.58	4.325%	$137.2708	$137.27	$137.25	$137.30
7 purchase totals =	$692.90		$735.7862	$735.78	$735.75	$735.70