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	$44.45	8.591%	$48.2687	$48.27	$48.25	$48.30
Purchase #2	$38.98	7.690%	$41.9776	$41.98	$42.00	$42.00
Purchase #3	$139.37	11.634%	$155.5843	$155.58	$155.60	$155.60
Purchase #4	$15.59	13.323%	$17.6671	$17.67	$17.65	$17.70
Purchase #5	$207.97	12.583%	$234.1389	$234.14	$234.15	$234.10
Purchase #6	$154.98	11.142%	$172.2479	$172.25	$172.25	$172.20
Purchase #7	$108.41	7.552%	$116.5971	$116.60	$116.60	$116.60
7 purchase totals =	$709.75		$786.4816	$786.49	$786.50	$786.50