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	$209.47	8.622%	$227.5305	$227.53	$227.55	$227.50
Purchase #2	$78.60	9.820%	$86.3185	$86.32	$86.30	$86.30
Purchase #3	$171.29	12.223%	$192.2268	$192.23	$192.25	$192.20
Purchase #4	$155.65	10.709%	$172.3186	$172.32	$172.30	$172.30
Purchase #5	$168.75	4.339%	$176.0721	$176.07	$176.05	$176.10
Purchase #6	$63.40	3.257%	$65.4649	$65.46	$65.45	$65.50
Purchase #7	$11.59	11.695%	$12.9455	$12.95	$12.95	$12.90
7 purchase totals =	$858.75		$932.8769	$932.88	$932.85	$932.80