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	$131.89	13.501%	$149.6965	$149.70	$149.70	$149.70
Purchase #2	$93.82	10.691%	$103.8503	$103.85	$103.85	$103.90
Purchase #3	$135.60	3.631%	$140.5236	$140.52	$140.50	$140.50
Purchase #4	$183.51	4.627%	$192.001	$192.00	$192.00	$192.00
Purchase #5	$171.47	8.414%	$185.8975	$185.90	$185.90	$185.90
Purchase #6	$95.51	8.467%	$103.5968	$103.60	$103.60	$103.60
Purchase #7	$243.32	4.756%	$254.8923	$254.89	$254.90	$254.90
7 purchase totals =	$1,055.12		$1,130.4580	$1,130.46	$1,130.45	$1,130.50