To convert the price to some other currency we need to select that currency in allowed currency and import currency rates from System->Manage currency ->Rates .
The synatx for currency conversion is currencyConvert($amount, $from, $to=null)
e.g:
Suppose we need convert Price from GBP(British Sterling Pound) to INR(Indian currency) then we need to write below code .
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$convertedPrice = Mage::helper('directory')->currencyConvert($price, GBP, INR);
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