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	$101.52	12.684%	$114.3968	$114.40	$114.40	$114.40
Purchase #2	$39.48	8.370%	$42.7845	$42.78	$42.80	$42.80
Purchase #3	$196.67	12.117%	$220.5005	$220.50	$220.50	$220.50
Purchase #4	$158.50	13.648%	$180.1321	$180.13	$180.15	$180.10
Purchase #5	$185.88	7.873%	$200.5143	$200.51	$200.50	$200.50
Purchase #6	$163.82	9.155%	$178.8177	$178.82	$178.80	$178.80
Purchase #7	$9.81	8.117%	$10.6063	$10.61	$10.60	$10.60
7 purchase totals =	$855.68		$947.7522	$947.75	$947.75	$947.70