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	$65.60	6.475%	$69.8476	$69.85	$69.85	$69.80
Purchase #2	$215.72	6.130%	$228.9436	$228.94	$228.95	$228.90
Purchase #3	$241.69	6.120%	$256.4814	$256.48	$256.50	$256.50
Purchase #4	$44.67	7.785%	$48.1476	$48.15	$48.15	$48.10
Purchase #5	$167.93	13.475%	$190.5586	$190.56	$190.55	$190.60
Purchase #6	$111.83	6.868%	$119.5105	$119.51	$119.50	$119.50
Purchase #7	$57.35	12.352%	$64.4339	$64.43	$64.45	$64.40
7 purchase totals =	$904.79		$977.9232	$977.92	$977.95	$977.80