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	$37.28	9.723%	$40.9047	$40.90	$40.90	$40.90
Purchase #2	$21.95	3.627%	$22.7461	$22.75	$22.75	$22.70
Purchase #3	$148.44	11.478%	$165.4779	$165.48	$165.50	$165.50
Purchase #4	$72.47	6.568%	$77.2298	$77.23	$77.25	$77.20
Purchase #5	$210.72	13.256%	$238.653	$238.65	$238.65	$238.70
Purchase #6	$35.39	11.284%	$39.3834	$39.38	$39.40	$39.40
Purchase #7	$21.46	4.632%	$22.454	$22.45	$22.45	$22.50
7 purchase totals =	$547.71		$606.8489	$606.84	$606.90	$606.90