Hi Jenny - we do not require receipts for transactions under $82.50 AUD including tax - equivalent to $55USD based on current rates.
My company requires receipts on all expenses that are not mileage, tips, or tolls, regarless of dollar amount. Another exception is fraudulent transactions and accidental personal charges. Other than that, receipts are required on everything.
We also do not have a minimum. We require receipts on everything except Mileage, tips, fraudulent charges, and airline charges that have level 3 data.