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	$75.32	13.709%	$85.6456	$85.65	$85.65	$85.60
Purchase #2	$153.83	8.587%	$167.0394	$167.04	$167.05	$167.00
Purchase #3	$28.90	8.273%	$31.2909	$31.29	$31.30	$31.30
Purchase #4	$158.61	7.105%	$169.8792	$169.88	$169.90	$169.90
Purchase #5	$91.65	13.159%	$103.7102	$103.71	$103.70	$103.70
Purchase #6	$19.55	10.778%	$21.6571	$21.66	$21.65	$21.70
Purchase #7	$134.39	6.757%	$143.4707	$143.47	$143.45	$143.50
7 purchase totals =	$662.25		$722.6931	$722.70	$722.70	$722.70