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	$195.76	11.605%	$218.4779	$218.48	$218.50	$218.50
Purchase #2	$10.25	3.699%	$10.6291	$10.63	$10.65	$10.60
Purchase #3	$198.52	3.710%	$205.8851	$205.89	$205.90	$205.90
Purchase #4	$73.60	10.455%	$81.2949	$81.29	$81.30	$81.30
Purchase #5	$153.62	12.861%	$173.3771	$173.38	$173.40	$173.40
Purchase #6	$132.82	4.754%	$139.1343	$139.13	$139.15	$139.10
Purchase #7	$40.47	5.793%	$42.8144	$42.81	$42.80	$42.80
7 purchase totals =	$805.04		$871.6128	$871.61	$871.70	$871.60