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	$138.38	11.177%	$153.8467	$153.85	$153.85	$153.80
Purchase #2	$93.63	7.536%	$100.686	$100.69	$100.70	$100.70
Purchase #3	$13.99	10.607%	$15.4739	$15.47	$15.45	$15.50
Purchase #4	$60.41	3.485%	$62.5153	$62.52	$62.50	$62.50
Purchase #5	$239.61	10.252%	$264.1748	$264.17	$264.15	$264.20
Purchase #6	$113.95	11.862%	$127.4667	$127.47	$127.45	$127.50
Purchase #7	$242.40	6.605%	$258.4105	$258.41	$258.40	$258.40
7 purchase totals =	$902.37		$982.5739	$982.58	$982.50	$982.60