The Default Currency is always set to 1.00 ...
Then you can hit Update to get the current settings for the exchange rates ...
Then in the Configuration ... My Store ...
Currency Conversion Ratio
When auto-updating currencies, what "uplift" ratio should be used to calculate the exchange rate used by your store?
ie: the bank rate is obtained from the currency-exchange servers; how much extra do you want to charge in order to make up the difference between the bank rate and the consumer rate?
Default: 1.05
This will cause the published bank rate to be multiplied by 1.05 to set the currency rates in your store.