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	$29.34	7.783%	$31.6235	$31.62	$31.60	$31.60
Purchase #2	$126.47	7.127%	$135.4835	$135.48	$135.50	$135.50
Purchase #3	$71.45	7.607%	$76.8852	$76.89	$76.90	$76.90
Purchase #4	$87.71	8.260%	$94.9548	$94.95	$94.95	$95.00
Purchase #5	$92.40	7.639%	$99.4584	$99.46	$99.45	$99.50
Purchase #6	$235.52	11.184%	$261.8606	$261.86	$261.85	$261.90
Purchase #7	$40.79	3.681%	$42.2915	$42.29	$42.30	$42.30
7 purchase totals =	$683.68		$742.5575	$742.55	$742.55	$742.70