You could choose not to publish the tally (or do you mean for votes that are required to be unanimous?), or agree beforehand not to disclose detailed-enough tallies to draw this conclusion (e.g. report only that 2 or fewer nay's were voted, but not whether that number was 0, 1, or 2.)
But more practically: I kind of doubt it matters when the vote is unanimous, because at that point you're in good company, and it's going to be hard for some external entity to blame you all too much (and if they do, it's easier to find backing for your position from all those that voted like you).
