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	$220.25	4.631%	$230.4498	$230.45	$230.45	$230.40
Purchase #2	$238.84	13.746%	$271.6709	$271.67	$271.65	$271.70
Purchase #3	$62.42	12.833%	$70.4304	$70.43	$70.45	$70.40
Purchase #4	$132.27	4.237%	$137.8743	$137.87	$137.85	$137.90
Purchase #5	$94.54	11.309%	$105.2315	$105.23	$105.25	$105.20
Purchase #6	$44.81	8.787%	$48.7475	$48.75	$48.75	$48.70
Purchase #7	$172.83	13.795%	$196.6719	$196.67	$196.65	$196.70
7 purchase totals =	$965.96		$1,061.0763	$1,061.07	$1,061.05	$1,061.00