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	$218.42	4.820%	$228.9478	$228.95	$228.95	$228.90
Purchase #2	$19.25	8.559%	$20.8976	$20.90	$20.90	$20.90
Purchase #3	$85.92	5.560%	$90.6972	$90.70	$90.70	$90.70
Purchase #4	$13.70	12.776%	$15.4503	$15.45	$15.45	$15.50
Purchase #5	$137.28	12.204%	$154.0337	$154.03	$154.05	$154.00
Purchase #6	$30.52	10.321%	$33.67	$33.67	$33.65	$33.70
Purchase #7	$40.52	10.238%	$44.6684	$44.67	$44.65	$44.70
7 purchase totals =	$545.61		$588.3650	$588.37	$588.35	$588.40