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	$42.51	13.749%	$48.3547	$48.35	$48.35	$48.40
Purchase #2	$53.39	10.618%	$59.059	$59.06	$59.05	$59.10
Purchase #3	$100.40	12.155%	$112.6036	$112.60	$112.60	$112.60
Purchase #4	$15.82	11.766%	$17.6814	$17.68	$17.70	$17.70
Purchase #5	$43.46	6.721%	$46.3809	$46.38	$46.40	$46.40
Purchase #6	$221.78	5.548%	$234.0844	$234.08	$234.10	$234.10
Purchase #7	$146.62	8.246%	$158.7103	$158.71	$158.70	$158.70
7 purchase totals =	$623.98		$676.8743	$676.86	$676.90	$677.00