fixed price not working

Hi,
I have installed the currency plugin on our website.
However, we are struggling with the “Fixed price” option.
We have created a product, and set a price in dollars: regular price=490$ sale price=360$
However when you save and then view the product page, it shows these prices:
($408.33) $300.00

The same happens with our GBP prices.

What’s going on there ?

Thanks ever so much for your help