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	$211.46	9.522%	$231.5952	$231.60	$231.60	$231.60
Purchase #2	$40.30	12.859%	$45.4822	$45.48	$45.50	$45.50
Purchase #3	$52.45	11.548%	$58.5069	$58.51	$58.50	$58.50
Purchase #4	$42.99	3.755%	$44.6043	$44.60	$44.60	$44.60
Purchase #5	$66.66	5.848%	$70.5583	$70.56	$70.55	$70.60
Purchase #6	$112.39	4.309%	$117.2329	$117.23	$117.25	$117.20
Purchase #7	$132.61	10.329%	$146.3073	$146.31	$146.30	$146.30
7 purchase totals =	$658.86		$714.2871	$714.29	$714.30	$714.30