That's true.  It's called Dynamic Currency Conversion (DCC).  MOST Credit Card companies charge a Foreign Transaction Fee, which applies on ALL Foreign transactions -- regardless of what currency they are charged in.  The 'Would you like that charge in dollars?" conversion rate is usually a fair bit higher than what most CC companies charge, as well.

Example:  Today's base rate (often referred to as the Inter-Bank Rate) is 1 Euro = $1.116.  The typical charge from most Credit Card companies would be around $1.14 - 1.15 PLUS a 1-4% Transaction fee (depending on the card).  A typical DCC rate would be around $1.17 - 1.18 and you would STILL be hit with the Transaction Fee. 

For more info on DCC, see:  https://en.wikipedia.org/wiki/Dynamic_currency_conversion  and http://ireland.activeboard.com/t43378621/question-about-exchange-rates-and-credit-cards/

Be happy -- I remember paying as much as $1.45 per Euro!