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	$230.90	10.598%	$255.3708	$255.37	$255.35	$255.40
Purchase #2	$122.83	5.169%	$129.1791	$129.18	$129.20	$129.20
Purchase #3	$106.84	5.606%	$112.8295	$112.83	$112.85	$112.80
Purchase #4	$97.26	6.160%	$103.2512	$103.25	$103.25	$103.30
Purchase #5	$70.46	4.870%	$73.8914	$73.89	$73.90	$73.90
Purchase #6	$20.29	5.428%	$21.3913	$21.39	$21.40	$21.40
Purchase #7	$221.85	10.843%	$245.9052	$245.91	$245.90	$245.90
7 purchase totals =	$870.43		$941.8185	$941.82	$941.85	$941.90