GridSnapping.cs | GameObject Editor Grid Snapping (Optional: change the float gridSize to set the size of the grid)

GridSnapping.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

[ExecuteInEditMode]
public class GridSnapping : MonoBehaviour
{
    public GameObject target;
    Vector3 gridPos;
    public float gridSize = 10f;

    private void Awake()
    {
        gridSize = target.transform.localScale.x * 10f;
    }

    void LateUpdate()
    {
        gridPos.x = Mathf.Floor(target.transform.position.x / gridSize) * gridSize;
        gridPos.y = Mathf.Floor(target.transform.position.y / gridSize) * gridSize;
        gridPos.z = Mathf.Floor(target.transform.position.z / gridSize) * gridSize;

        target.transform.position = gridPos;
    }   
}