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	$57.82	12.839%	$65.2435	$65.24	$65.25	$65.20
Purchase #2	$9.43	8.243%	$10.2073	$10.21	$10.20	$10.20
Purchase #3	$158.88	4.505%	$166.0375	$166.04	$166.05	$166.00
Purchase #4	$10.40	4.389%	$10.8565	$10.86	$10.85	$10.90
Purchase #5	$129.68	13.229%	$146.8354	$146.84	$146.85	$146.80
Purchase #6	$12.85	6.251%	$13.6533	$13.65	$13.65	$13.70
Purchase #7	$109.38	9.533%	$119.8072	$119.81	$119.80	$119.80
7 purchase totals =	$488.44		$532.6407	$532.65	$532.65	$532.60