That would be what I would do. If you can snug the cabinets up side to side it will be just fine. If you can't snug them precisely, and end up with a gap less than 1/8", you could leave a 1/8" or a 1/16" overlap on the outsides.
I have used a 1/4" plywood spacer between cabinets to close a gap since most production cabinets have a 1/8" or so, overhang on the outside.
The answer to your question will only be as detailed and specific as the question is detailed and specific. Good questions also include a sketch or a photo that illustrates your issue. (:< D)
Last edited by woodnthings; 06-02-2017 at 08:50 AM.