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	$139.97	8.443%	$151.7877	$151.79	$151.80	$151.80
Purchase #2	$92.34	6.641%	$98.4723	$98.47	$98.45	$98.50
Purchase #3	$132.80	8.149%	$143.6219	$143.62	$143.60	$143.60
Purchase #4	$246.96	4.691%	$258.5449	$258.54	$258.55	$258.50
Purchase #5	$141.82	11.562%	$158.2172	$158.22	$158.20	$158.20
Purchase #6	$40.61	5.689%	$42.9203	$42.92	$42.90	$42.90
Purchase #7	$92.97	9.209%	$101.5316	$101.53	$101.55	$101.50
7 purchase totals =	$887.47		$955.0959	$955.09	$955.05	$955.00