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	$111.29	9.848%	$122.2498	$122.25	$122.25	$122.20
Purchase #2	$144.35	4.825%	$151.3149	$151.31	$151.30	$151.30
Purchase #3	$192.27	6.671%	$205.0963	$205.10	$205.10	$205.10
Purchase #4	$60.53	10.176%	$66.6895	$66.69	$66.70	$66.70
Purchase #5	$97.37	8.387%	$105.5364	$105.54	$105.55	$105.50
Purchase #6	$141.27	13.172%	$159.8781	$159.88	$159.90	$159.90
Purchase #7	$68.59	4.166%	$71.4475	$71.45	$71.45	$71.40
7 purchase totals =	$815.67		$882.2125	$882.22	$882.25	$882.10