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	$240.30	5.536%	$253.603	$253.60	$253.60	$253.60
Purchase #2	$55.89	5.724%	$59.0891	$59.09	$59.10	$59.10
Purchase #3	$68.73	10.810%	$76.1597	$76.16	$76.15	$76.20
Purchase #4	$233.83	13.850%	$266.2155	$266.22	$266.20	$266.20
Purchase #5	$122.95	13.566%	$139.6294	$139.63	$139.65	$139.60
Purchase #6	$19.60	7.504%	$21.0708	$21.07	$21.05	$21.10
Purchase #7	$137.39	8.163%	$148.6051	$148.61	$148.60	$148.60
7 purchase totals =	$878.69		$964.3726	$964.38	$964.35	$964.40