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	$173.25	4.523%	$181.0861	$181.09	$181.10	$181.10
Purchase #2	$156.57	10.380%	$172.822	$172.82	$172.80	$172.80
Purchase #3	$221.87	13.772%	$252.4259	$252.43	$252.45	$252.40
Purchase #4	$136.35	7.696%	$146.8435	$146.84	$146.85	$146.80
Purchase #5	$108.41	10.433%	$119.7204	$119.72	$119.70	$119.70
Purchase #6	$49.43	4.208%	$51.51	$51.51	$51.50	$51.50
Purchase #7	$203.75	13.404%	$231.0607	$231.06	$231.05	$231.10
7 purchase totals =	$1,049.63		$1,155.4686	$1,155.47	$1,155.45	$1,155.40