Toddler tantrums

My 2 (almost 3) year old is having tantrums ALL the time. And I’m a FTM, and I’m not sure how I should handle them. A lot of the times, he cries and SCREAMS because I won’t let him get a new car at Walmart. It drives me crazy. He doesn’t need a new one every time we go to the store. I try to ignore it, but he can go on for over 20 minutes. How do you guys deal with it? Sometimes he even screams and then just pees himself. (He is fully potty trained) what are your guys ways to deal with toddler tantrums?