Calculating County taxes

[kevgos]

Disclaimer: I've searched the site and found similar, but not exact, situations, so I thought I'd ask for myself.

I live in a state (Wisconsin) where tax is calculated by county. Not zip code, not city, but COUNTY. I found a bunch of addons and general "whatnot" to calculate taxes based on city, zip code, or whatever else - which, as I said, does me little to no good. So, after some deep internet searching, I found some code:

//put the delivery address together for Google's URL
$street = $order->delivery['address'];
$city = $order->delivery['city'];
$state = $order->delivery['state'];
$zip = $order->delivery['zip'];
$mapaddress = urlencode("$street $city $state $zip");
//Your Google Maps API key
$key = "APIKEY";
// Desired URL
$address = "http://maps.google.com/maps/geo?q=$mapaddress&output=xml&key=$key";
// Retrieve the URL contents
$page = file_get_contents($address);
// Parse the returned XML file
$xml = new SimpleXMLElement($page);
// Retrieve the desired XML node
$county = trim($xml->Response->Placemark->AddressDetails->
Country->AdministrativeArea->SubAdministrativeArea->
SubAdministrativeAreaName);

My questions are, first, if this is actually "recommended" or not, and if so, where does it go? Thanks!