Yes Hugh, I have found that they will work being a half bubble off front to rear and side to side but perfect level is best. Not as critical when hooked to power. I like to have a bubble level in the freezer compartment.
The manufacturers today say that within three degrees is close enough. The rule of thumb is that if you can walk comfortably the refrigerator will be happy. You no longe need to level the RV by the refrigerator shelf.