Is it possible to convert an integer to a Vector3?

using UnityEngine;
using System.Collections;
public class grasstestdelete : MonoBehaviour {
	// Use this for initialization
	void Start () {
		//Debug.Log(Mathf.RoundToInt(10.7F));
	// Update is called once per frame
	void Update () {
		transform.position = Mathf.RoundToInt (gameObject.transform.position.x);
		//transform.position = Mathf.RoundToInt (gameObject.transform.position.y);
		//transform.position = Mathf.RoundToInt (gameObject.transform.position.z);
              
well if you wanted to do this right, you would have to get a copy of the Vector3, change the vectors and pass it back.
using your code and modifying:
using UnityEngine;
using System.Collections;
public class grasstestdelete : MonoBehaviour {
    // Use this for initialization
    void Start () {
        //Debug.Log(Mathf.RoundToInt(10.7F));
    // Update is called once per frame
    void Update () {
			Vector3 pos = transform.position; // get a copy
			pos.x = Mathf.RoundToInt(gameObject.transform.position.x);
			pos.y = Mathf.RoundToInt(gameObject.transform.position.y);
			pos.z = Mathf.RoundToInt(gameObject.transform.position.z);
			transform.position = pos; // now put it back and override the vector3 with the new one.