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	$120.47	11.622%	$134.471	$134.47	$134.45	$134.50
Purchase #2	$107.60	9.388%	$117.7015	$117.70	$117.70	$117.70
Purchase #3	$47.53	6.458%	$50.5995	$50.60	$50.60	$50.60
Purchase #4	$116.87	8.785%	$127.137	$127.14	$127.15	$127.10
Purchase #5	$54.44	12.192%	$61.0773	$61.08	$61.10	$61.10
Purchase #6	$100.27	5.680%	$105.9653	$105.97	$105.95	$106.00
Purchase #7	$139.72	8.450%	$151.5263	$151.53	$151.55	$151.50
7 purchase totals =	$686.90		$748.4779	$748.49	$748.50	$748.50