Yeah, 5/8" to 3/4" is about a 3mm jump. You can find lots of in between sizes on bodyartforms.com.
Here's an example of a pair of tunnels that comes in 5/8", 17mm, and 11/16":http://www.bodyartforms.com/productdetails.asp?keywords=&jewelry=&gauge=17mm&flare_type=&length=&brand=&price=&material=&button=%C2%BB+Submit+filter+%C2%AB&date=&restock=&new=&orderby=&RecordDisplay=&Filter=Yes&Extras=&Retainer=&Showout=&Threading=&preorders=&ProductID=2900&index=7
If your ears are ready to stretch, at small jumps like that you probably won't even need tape or tapers. I haven't used tapers or tape since 4G.