- Open
Photoshop > Preferences > Guides, Grid, Slices & Count... - In the Grid section, set: Gridline every 10 pixels, subdivisions 10.
- Make sure
View > Show > Gridis✓or-. It seems to be a bug in photoshop, but snapping to grid doesn't work when the grid is enabled but hidden. If you find the grid distracting, you can set it to "Dots" in prefs. - Make sure
View > Snapis✓. - Make sure
View > Snap To > Gridis✓.
Now, if you show extras (that's View > Extras or Cmd-H or maybe Cmd-Ctrl-H) everything will snap to pixel boundaries.
If you hide extras, some tools will work subpixel.
Note: I run CS3 so I don't know if this still works on CS4 or CS5. It probably does.