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	$44.85	7.423%	$48.1792	$48.18	$48.20	$48.20
Purchase #2	$18.59	6.508%	$19.7998	$19.80	$19.80	$19.80
Purchase #3	$223.34	13.272%	$252.9817	$252.98	$253.00	$253.00
Purchase #4	$53.51	10.517%	$59.1376	$59.14	$59.15	$59.10
Purchase #5	$237.89	7.335%	$255.3392	$255.34	$255.35	$255.30
Purchase #6	$123.45	8.217%	$133.5939	$133.59	$133.60	$133.60
Purchase #7	$33.86	7.548%	$36.4158	$36.42	$36.40	$36.40
7 purchase totals =	$735.49		$805.4472	$805.45	$805.50	$805.40