I'm not sure about the $5 cheapies nor would I trust it when I'm working on stuff that costs 10-20x (or more) that price to replace.
I have the one below. It has worked great for me and it doesn't break the bank. Keep in mind that when testing certain sensors you will need to know the air temperature and some tests require you to put the sensors in water that you need to know the temp of as well. This multimeter allows you to do all of this.
Digital Multimeter with Manual Ranging, 8-Function- Craftsman-Tools-Electricians Tools & Lighting-Multi-Meters & Meters