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	$97.33	8.495%	$105.5982	$105.60	$105.60	$105.60
Purchase #2	$93.63	5.382%	$98.6692	$98.67	$98.65	$98.70
Purchase #3	$34.50	3.495%	$35.7058	$35.71	$35.70	$35.70
Purchase #4	$105.98	4.755%	$111.0193	$111.02	$111.00	$111.00
Purchase #5	$77.71	6.848%	$83.0316	$83.03	$83.05	$83.00
Purchase #6	$149.77	13.849%	$170.5116	$170.51	$170.50	$170.50
Purchase #7	$73.97	10.655%	$81.8515	$81.85	$81.85	$81.90
7 purchase totals =	$632.89		$686.3872	$686.39	$686.35	$686.40