Setting Input field to 2 decimal points (Price)

I am currently trying to input prices into a .txt file. So i want it when the user input:1.1 Instead of 1.1, I want it to become 1.10 instead. As it would look better for the table I am trying to make in the future. I would also like to round up or down if it goes more than 3 decimal places. (_Thanks john1024 for the correction_)