Is it normal for Safari tabs to use 1 GB ram? Less than one hour ago I opened a few tabs on Safari. One of them is using 1 GB of ram for some reason. It's version 13.0.5. 

What are the reasons behind this? Should I shut it down? Restart? Clear caches?
Safari can be a resource hog, particularly if you have a lot of tabs or windows open to graphics-intense sites, so this doesn't actually surprise me. If you turn on the 'Compressed Memory' column in Activity Monitor — from the menu bar: View → Colums → Compressed Memory — you'll likely see that that most of this memory usage is stuff that's been compressed and shunted off to virtual memory until it's needed.

For a comparison, I've been doing a lot of AppleScripting recently and so Activity Monitor reports that Script Editor is taking up 3.39 Gb of memory, with 2.79 Gb in compressed VM storage. MacOS has sophisticated memory management; as long as you're not seeing strange behavior — e.g. slower than normal response times — you shouldn't have to worry about it.