Problems with the Price shown in Checkout

Hello

We`ve built a Store for our customers. We always had problems with the Curcy Plugin / Prices ( EUR ). So we have made Fixed Prices for the Customer.
Now the EUR Prices looks better, but at the checkout and also on the invoice another price is displayed.

Information:
– Multi currency Plugin
– Pgae http://www.friloswissmade.com
– CHF ( Main Currency ), EUR ( Currency ) used
– Fixed Prices
– Prices incl. Tax
– PDF invoice & Packing slip Plugin in use

EXAMPLE:
CHF Price = 259.- (Correct)
EUR (Fixed Price = 249.- (Correct)
Checkout Price = 270.70 EUR (incorrect)

We would love to fix the problem for our customer, but there is no chance to change the checkout displayed prices.

Kind regards