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	$50.33	6.170%	$53.4354	$53.44	$53.45	$53.40
Purchase #2	$6.77	13.209%	$7.6642	$7.66	$7.65	$7.70
Purchase #3	$135.51	7.812%	$146.096	$146.10	$146.10	$146.10
Purchase #4	$90.81	10.222%	$100.0926	$100.09	$100.10	$100.10
Purchase #5	$65.86	13.762%	$74.9237	$74.92	$74.90	$74.90
Purchase #6	$16.33	12.845%	$18.4276	$18.43	$18.45	$18.40
Purchase #7	$224.34	3.230%	$231.5862	$231.59	$231.60	$231.60
7 purchase totals =	$589.95		$632.2257	$632.23	$632.25	$632.20