How to cuntry code respect to set currency

LINK:- http://rosskendall.com/blog/web/using-geoip-with-magento-and-multiple-sites


code:- //GeoIP Track
define("GEOIP_DAT_FILE", "geoip/GeoIP.dat");
define("GEOIP_INC_FILE", "geoip/geoip.inc");

include(GEOIP_INC_FILE);

$_geoip = geoip_open(GEOIP_DAT_FILE ,GEOIP_STANDARD);
$_country_code = geoip_country_code_by_addr($_geoip, $_SERVER['REMOTE_ADDR']);

geoip_close($_geoip);

switch ($_country_code) {
  case "GB": // United Kingdom
    $_SERVER["MAGE_RUN_CODE"] = "uk";
    break;
  case "AU": // Australia
    $_SERVER["MAGE_RUN_CODE"] = "au";
    break;
  case "NZ": // New Zealand
    $_SERVER["MAGE_RUN_CODE"] = "nz";
    break;
  default:
    $_SERVER["MAGE_RUN_CODE"] = "";
}