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	$237.37	11.858%	$265.5173	$265.52	$265.50	$265.50
Purchase #2	$164.83	10.863%	$182.7355	$182.74	$182.75	$182.70
Purchase #3	$151.95	9.102%	$165.7805	$165.78	$165.80	$165.80
Purchase #4	$140.61	4.450%	$146.8671	$146.87	$146.85	$146.90
Purchase #5	$160.59	6.126%	$170.4277	$170.43	$170.45	$170.40
Purchase #6	$186.39	5.429%	$196.5091	$196.51	$196.50	$196.50
Purchase #7	$155.75	3.738%	$161.5719	$161.57	$161.55	$161.60
7 purchase totals =	$1,197.49		$1,289.4091	$1,289.42	$1,289.40	$1,289.40