I put Paraguay in the parameters during the install process and the Guarani currency have been automatically implemented and put as default currency.
As I buy my products in $, I put back $ as default currency. I create a new product with his price in $, and in the web site, when I put the price in Guaranies, even with the change currency put to 4200 the price in Gs stay the same as in $ as if the change was 1:1.
But when i put the Guarani as default currency and put 0.00024 as change in $ the conversion is well done.
I solved the problem erasing the Guarani currency and create it back.