Scripts for snapping to virtual pixel boundaries in low-rez Unity games. made for use with 2D Toolkit-- for Unity 2D, change the metersPerPixel calculation.

Extensions.cs

using UnityEngine;

namespace FBD
{
	public static class Extensions
	{
		public static Transform FindInHierarchy(this Transform t, string name)
		{
			for (int c = 0; c < t.childCount; c++)
			{
				Transform temp = t.GetChild(c);
				if (temp.name == name)
					return temp;
				else
				{
					temp = temp.FindInHeirarchy(name);
					if (temp != null)
						return temp;
				}
			}
			
			return null;
		}
		
		public static float RoundTo(float number, float roundTo)
		{
			return Mathf.Round(number / roundTo) * roundTo;
		}
	}
}

PixelSnap.cs

using UnityEngine;
using System.Collections.Generic;

namespace FBD
{
	public class PixelSnap : MonoBehaviour
	{
		private float metersPerPixel;
		private Vector3 realPosition = Vector3.zero;

		// Use this for initialization
		void Start()
		{
			PixelSnapCamera.RegisterSnapObject(this);
			metersPerPixel = 1.0f / Camera.main.GetComponent<tk2dCamera>().CameraSettings.orthographicPixelsPerMeter;
		}

		void OnDestroy()
		{
			PixelSnapCamera.UnRegisterSnapObject(this);
		}

		public void PrepareRender()
		{
			realPosition = transform.position;
			Vector3 temp = new Vector3(Extensions.RoundTo(transform.position.x, metersPerPixel),
						Extensions.RoundTo(transform.position.y, metersPerPixel), 0f);
			transform.position = temp;
		}

		public void PostRender()
		{
			transform.position = realPosition;
		}
	}
}

PixelSnapCamera.cs

using UnityEngine;
using System.Collections.Generic;

namespace FBD
{
	public class PixelSnapCamera : MonoBehaviour
	{
		private static List<PixelSnap> snapObjects;

		void Start()
		{
			if (snapObjects == null)
				snapObjects = new List<PixelSnap>();
		}

		void OnPreCull()
		{
			foreach (PixelSnap p in snapObjects)
				p.PrepareRender();
		}

		void OnPostRender()
		{
			foreach (PixelSnap p in snapObjects)
				p.PostRender();
		}

		public static void RegisterSnapObject(PixelSnap snapObj)
		{
			snapObjects.Add(snapObj);
		}

		public static void UnRegisterSnapObject(PixelSnap snapObj)
		{
			snapObjects.Remove(snapObj);
		}
	}
}