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	$126.50	8.786%	$137.6143	$137.61	$137.60	$137.60
Purchase #2	$152.98	9.703%	$167.8236	$167.82	$167.80	$167.80
Purchase #3	$72.60	7.189%	$77.8192	$77.82	$77.80	$77.80
Purchase #4	$120.99	4.144%	$126.0038	$126.00	$126.00	$126.00
Purchase #5	$131.93	4.476%	$137.8352	$137.84	$137.85	$137.80
Purchase #6	$217.59	13.476%	$246.9124	$246.91	$246.90	$246.90
Purchase #7	$105.32	13.472%	$119.5087	$119.51	$119.50	$119.50
7 purchase totals =	$927.91		$1,013.5172	$1,013.51	$1,013.45	$1,013.40