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	$121.88	10.432%	$134.5945	$134.59	$134.60	$134.60
Purchase #2	$221.38	4.616%	$231.5989	$231.60	$231.60	$231.60
Purchase #3	$167.57	10.110%	$184.5113	$184.51	$184.50	$184.50
Purchase #4	$215.83	7.285%	$231.5532	$231.55	$231.55	$231.60
Purchase #5	$81.82	10.792%	$90.65	$90.65	$90.65	$90.70
Purchase #6	$94.87	8.863%	$103.2783	$103.28	$103.30	$103.30
Purchase #7	$134.67	6.324%	$143.1865	$143.19	$143.20	$143.20
7 purchase totals =	$1,038.02		$1,119.3727	$1,119.37	$1,119.40	$1,119.50