In Uruguay if you use cash you won't benefit from VAT reductions for foreign tourists in for instance restaurants. In the past these reductions have been quite high (approximately 20%) but were reduced to "only" 9% on May 1st.
If you pay with VISA, the VAT is reduced when you pay, with MasterCard you get the VAT reduction credited to your account after 2-3 days. This was this past January.
The withdrawal limits I saw at ATMs were 5000 UYU (now 173 USD) or 300 USD (same ATM). Had no problem withdrawing 3*5000 UYU. I can't remember how much the Uruguayan bank took so it cannot have been that much.
All stores that accept cards must do so regardless of the total amount, so I used very little cash.