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	$14.63	6.314%	$15.5537	$15.55	$15.55	$15.60
Purchase #2	$13.27	9.325%	$14.5074	$14.51	$14.50	$14.50
Purchase #3	$64.85	10.177%	$71.4498	$71.45	$71.45	$71.40
Purchase #4	$126.46	10.533%	$139.78	$139.78	$139.80	$139.80
Purchase #5	$70.27	13.574%	$79.8084	$79.81	$79.80	$79.80
Purchase #6	$173.38	4.493%	$181.17	$181.17	$181.15	$181.20
Purchase #7	$95.25	13.545%	$108.1516	$108.15	$108.15	$108.20
7 purchase totals =	$558.11		$610.4209	$610.42	$610.40	$610.50