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	$123.41	6.857%	$131.8722	$131.87	$131.85	$131.90
Purchase #2	$170.87	11.660%	$190.7934	$190.79	$190.80	$190.80
Purchase #3	$184.74	8.498%	$200.4392	$200.44	$200.45	$200.40
Purchase #4	$126.93	13.821%	$144.473	$144.47	$144.45	$144.50
Purchase #5	$238.94	3.254%	$246.7151	$246.72	$246.70	$246.70
Purchase #6	$34.64	12.819%	$39.0805	$39.08	$39.10	$39.10
Purchase #7	$12.56	12.646%	$14.1483	$14.15	$14.15	$14.10
7 purchase totals =	$892.09		$967.5217	$967.52	$967.50	$967.50