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	$42.80	12.255%	$48.0451	$48.05	$48.05	$48.00
Purchase #2	$203.89	13.131%	$230.6628	$230.66	$230.65	$230.70
Purchase #3	$137.94	4.104%	$143.6011	$143.60	$143.60	$143.60
Purchase #4	$225.74	12.155%	$253.1787	$253.18	$253.20	$253.20
Purchase #5	$227.82	6.190%	$241.9221	$241.92	$241.90	$241.90
Purchase #6	$72.57	8.125%	$78.4663	$78.47	$78.45	$78.50
Purchase #7	$138.48	3.815%	$143.763	$143.76	$143.75	$143.80
7 purchase totals =	$1,049.24		$1,139.6391	$1,139.64	$1,139.60	$1,139.70