Why is not making the correct currency exchange at checkout page

Hi I have a problem with the woocommerce multi currency plugin.

My payment method is Paypal which only accepts dollars. So When I add to cart a product in any currency other than dollars(for example CRC – Colon Costarricense) and proceed to checkout, the price to pay for the product in the subtotal does not change to dollars according to my established exchange rates.

Please help me.

I attached my currency options and the checkout tab configuration.