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	$137.84	7.827%	$148.6287	$148.63	$148.65	$148.60
Purchase #2	$133.31	4.533%	$139.3529	$139.35	$139.35	$139.40
Purchase #3	$118.90	7.187%	$127.4453	$127.45	$127.45	$127.40
Purchase #4	$151.75	7.796%	$163.5804	$163.58	$163.60	$163.60
Purchase #5	$78.26	6.763%	$83.5527	$83.55	$83.55	$83.60
Purchase #6	$60.43	10.695%	$66.893	$66.89	$66.90	$66.90
Purchase #7	$203.34	13.603%	$231.0003	$231.00	$231.00	$231.00
7 purchase totals =	$883.83		$960.4533	$960.45	$960.50	$960.50