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	$57.28	9.603%	$62.7806	$62.78	$62.80	$62.80
Purchase #2	$17.49	5.696%	$18.4862	$18.49	$18.50	$18.50
Purchase #3	$15.77	13.385%	$17.8808	$17.88	$17.90	$17.90
Purchase #4	$42.99	13.548%	$48.8143	$48.81	$48.80	$48.80
Purchase #5	$85.75	5.715%	$90.6506	$90.65	$90.65	$90.70
Purchase #6	$143.32	12.379%	$161.0616	$161.06	$161.05	$161.10
Purchase #7	$241.67	10.738%	$267.6205	$267.62	$267.60	$267.60
7 purchase totals =	$604.27		$667.2946	$667.29	$667.30	$667.40