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	$70.27	9.500%	$76.9457	$76.95	$76.95	$76.90
Purchase #2	$95.74	7.626%	$103.0411	$103.04	$103.05	$103.00
Purchase #3	$139.49	13.160%	$157.8469	$157.85	$157.85	$157.80
Purchase #4	$38.73	5.584%	$40.8927	$40.89	$40.90	$40.90
Purchase #5	$38.58	11.182%	$42.894	$42.89	$42.90	$42.90
Purchase #6	$38.74	13.250%	$43.8731	$43.87	$43.85	$43.90
Purchase #7	$161.74	7.628%	$174.0775	$174.08	$174.10	$174.10
7 purchase totals =	$583.29		$639.5710	$639.57	$639.60	$639.50