You can use the snapping scale if you press Ctrl while you are scaling, moving or rotating it in any axis.
If you need the snap to be always on, you can toggle on the icon that is on the top of the game viewport. Check the image below:
Note that the snap is not relative to the grid, but relative to the objects initial transform.
You can also snap using lower values if you press Ctrl + Shift while transforming your object.
Check the following table to see the snapping values of each method and each transform.
I work using the 2D viewport and I don’t see the “Transform” option there. Sadly, such a luxury seems to be 3D-exclusive (I checked the 3D viewport and the Transform thing showed up. Went back to 2D and it disappeared).
That is not a 3D only feature as @EX74 mentioned and showed you in his reply. In fact there are some good tutorials to get started with the Godot viewport if you do an easy google (or any other search engine) search.
I will post a good tutorial I found just by searching in google“godot 4 snapping viewport tutorial”.
I hope it helps. And remember, Google is your friend when it comes to learning new stuff