If it's the MS, not an audit, I have done many. HOWEVER, they recently added requirements of photos for any negatives you see -- and you have to take them without being seen! Even if everyone IS carrying a cell phone nowadays, they aren't walking around inside a store taking multiple photos with it.
Not too much work, if it's really really close by, or if you're going right by the location anyway.
I understand the reimbursement has also been lowered recently. Previously, $5 in gas, up to $2 for inside purchase, now $3 and $1 (IIRC).