Monetary currency on Tatooine

In STAR WARS EPISODE 1 (THE PHANTOM MENACE), Wattoo the Toydarian junk dealer would not accept Qui-Gon Jinn's Republic credits as payment for the parts Qui-Gon needed to repair Amidala's Naboo cruiser. Wattoo said that Republic credits were not an accepted currency on Tatooine. Did this change by the time the Empire took over? Were the denizens of Tatooine using Imperial currency by the time of the Original Trilogy?

If neither Republic nor Imperial credits were ever used on Tatooine, then what *did* the people of Tatooine use as a medium of exchange? Was it a pure barter system, or did Tatooine have its own currency (possibly issued by the Hutts)?

 

There's an EU defined Hutt Credit that was used on Tatooine. It's called a Wiuppi or something like that.

I would imagine there were some people and places that took Republic/Imperial credits. Likely not at the current exchange rate though.

 

I would imagine they did a lot of trading.

 

I believe that Tatooine was initially a Republic planet, but as the Republic got overstreched and corrupt and Tatooine fell out of it's influence. The Hutts move in and are in control. But then the Empire comes on the scene and dominates the whole galaxy.