Actually, you can create your own script that will go through all GameObjects in the scene and round their coordinates to whole numbers :) To be able to call a method from the inspector, use ContextMenu attribute, and then you will be able to click on the three vertical dots next to the name of the component. Here is a snippet:
[ContextMenu(nameof(RoundPositions))]
public void RoundPositions()
{/*Round all positions of gameObjects in the Scene to whole numbers*/}