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	$188.96	11.457%	$210.6091	$210.61	$210.60	$210.60
Purchase #2	$118.81	13.518%	$134.8707	$134.87	$134.85	$134.90
Purchase #3	$34.28	10.823%	$37.9901	$37.99	$38.00	$38.00
Purchase #4	$13.27	5.243%	$13.9657	$13.97	$13.95	$14.00
Purchase #5	$56.57	8.661%	$61.4695	$61.47	$61.45	$61.50
Purchase #6	$58.27	13.189%	$65.9552	$65.96	$65.95	$66.00
Purchase #7	$177.28	10.716%	$196.2773	$196.28	$196.30	$196.30
7 purchase totals =	$647.44		$721.1376	$721.15	$721.10	$721.30