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	$33.68	12.380%	$37.8496	$37.85	$37.85	$37.80
Purchase #2	$25.59	7.184%	$27.4284	$27.43	$27.45	$27.40
Purchase #3	$162.55	12.725%	$183.2345	$183.23	$183.25	$183.20
Purchase #4	$126.61	13.599%	$143.8277	$143.83	$143.85	$143.80
Purchase #5	$12.34	10.161%	$13.5939	$13.59	$13.60	$13.60
Purchase #6	$91.43	12.222%	$102.6046	$102.60	$102.60	$102.60
Purchase #7	$203.38	10.173%	$224.0698	$224.07	$224.05	$224.10
7 purchase totals =	$655.58		$732.6085	$732.60	$732.65	$732.50