how do I set the calculator to operate only with 2 decimals?

There's a difference between working with two decimal places and displaying with two decimal places.  It's dangerous to do the former!  Errors build up quickly.  To display x to two decimal places you can do:  round(100x)/100.

We round the thousandths place and that number will become the number that you want with 2 deciamls for example 1/7=0.14258...≈0.142≈0.14