Don't slip the 5sts off the left hand needle. Knit the 5sts tog tbl but leave them on the left hand needle. You'll have one loop over the right needle. Do a yarn over on the right needle and then re-insert the right needle into the same 5sts on the left needle. Do another yo on the right needle and again re-insert the right needle into the same 5sts on the left needle, knit them tog tbl and this time drop the sts from the left needle.
If you're a tight knitter, the k5tog won't be easy so try to loosen un on these sts.
Actually, this might be easier with a crochet hook. I've used one to knit large numbers of sts together.