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	$192.46	13.204%	$217.8724	$217.87	$217.85	$217.90
Purchase #2	$52.94	3.571%	$54.8305	$54.83	$54.85	$54.80
Purchase #3	$108.90	13.674%	$123.791	$123.79	$123.80	$123.80
Purchase #4	$152.86	8.244%	$165.4618	$165.46	$165.45	$165.50
Purchase #5	$205.91	10.611%	$227.7591	$227.76	$227.75	$227.80
Purchase #6	$9.47	12.750%	$10.6774	$10.68	$10.70	$10.70
Purchase #7	$115.59	3.331%	$119.4403	$119.44	$119.45	$119.40
7 purchase totals =	$838.13		$919.8325	$919.83	$919.85	$919.90