I hope they would also implement accepting BTC all over the world. It would be a big help, but the government will not approved i'm sure. Keep up El Salvador nice improvement. How would they manage tax? 
I think you are interested in income tax. Check table with El Salvador taxes. Everything remains the same. Only foreign investors are free from paying taxes from deals with Bitcoin.
El Salvador still stick to US dollars and recalculate everything into it. Bitcoin is just another payment option. If someone pays them in Bitcoin, Euro, Swiss Frank, British Pound, bookkeepers will still exchange it into USD, put it into records and pay the tax.