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	$161.61	13.848%	$183.9898	$183.99	$184.00	$184.00
Purchase #2	$173.87	6.598%	$185.3419	$185.34	$185.35	$185.30
Purchase #3	$147.55	4.176%	$153.7117	$153.71	$153.70	$153.70
Purchase #4	$234.38	3.508%	$242.6021	$242.60	$242.60	$242.60
Purchase #5	$127.68	12.679%	$143.8685	$143.87	$143.85	$143.90
Purchase #6	$74.86	10.165%	$82.4695	$82.47	$82.45	$82.50
Purchase #7	$65.66	3.260%	$67.8005	$67.80	$67.80	$67.80
7 purchase totals =	$985.61		$1,059.7840	$1,059.78	$1,059.75	$1,059.80