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	$134.47	10.423%	$148.4858	$148.49	$148.50	$148.50
Purchase #2	$225.29	13.260%	$255.1635	$255.16	$255.15	$255.20
Purchase #3	$154.49	4.134%	$160.8766	$160.88	$160.90	$160.90
Purchase #4	$49.61	3.859%	$51.5244	$51.52	$51.50	$51.50
Purchase #5	$111.95	8.226%	$121.159	$121.16	$121.15	$121.20
Purchase #6	$220.51	3.103%	$227.3524	$227.35	$227.35	$227.40
Purchase #7	$198.43	8.301%	$214.9017	$214.90	$214.90	$214.90
7 purchase totals =	$1,094.75		$1,179.4634	$1,179.46	$1,179.45	$1,179.60