iTunes uses 4 fields to determine which albums sort together:
- Album
- Album Artist
- Sort Album
- Sort Album Artist
As long as all tracks have matching information in those tags, the album will sort together. So for albums with various artists, put the individual artist name in the Artist field, and put "Various Artists" in the Album Artist and Sort Album Artist fields. The album will sort together. If it doesn't immediately, remove the album from your library and re-add it.