Just got my credit card statement from Bali (which I used to pay for some things like waterbom park) I thought this info might be helpful to others. I did hear of somebodies card being scanned in Bali so was careful to use only at larger companies.
The exchange rate seems to have been 6450 which was typical for on the street conversion during our stay.
To pay for a family of 4 into waterbom park calculated to $72.68AU
To come back for the second day for the 4 was $24.60
Each time I did a cash withdrawal the back charge was $1.50
I paid at WAterbom Park, Mataharis and one of the hotels with my card without any problems - however, on the last day when I tried to do a cash withdrawal and it was unable to process - I had a mini panic attack thinking my card might have been compromised - but it must have just been that the line was down or something.
Anyhow I thought this info might be helpful to others thinking of using a credit card or wondering what sort of charges etc might be applied.