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	$238.31	7.345%	$255.8139	$255.81	$255.80	$255.80
Purchase #2	$235.42	5.172%	$247.5959	$247.60	$247.60	$247.60
Purchase #3	$14.78	5.296%	$15.5627	$15.56	$15.55	$15.60
Purchase #4	$145.25	8.497%	$157.5919	$157.59	$157.60	$157.60
Purchase #5	$106.47	11.763%	$118.9941	$118.99	$119.00	$119.00
Purchase #6	$225.83	12.242%	$253.4761	$253.48	$253.50	$253.50
Purchase #7	$7.55	3.316%	$7.8004	$7.80	$7.80	$7.80
7 purchase totals =	$973.61		$1,056.8350	$1,056.83	$1,056.85	$1,056.90