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	$153.26	13.301%	$173.6451	$173.65	$173.65	$173.60
Purchase #2	$37.47	6.776%	$40.009	$40.01	$40.00	$40.00
Purchase #3	$238.38	10.107%	$262.4731	$262.47	$262.45	$262.50
Purchase #4	$144.52	9.743%	$158.6006	$158.60	$158.60	$158.60
Purchase #5	$18.72	5.333%	$19.7183	$19.72	$19.70	$19.70
Purchase #6	$59.60	3.732%	$61.8243	$61.82	$61.80	$61.80
Purchase #7	$31.53	13.638%	$35.8301	$35.83	$35.85	$35.80
7 purchase totals =	$683.48		$752.1005	$752.10	$752.05	$752.00