It's no problem. You put up an item like a fruit or flower up for sale at Re-Tail for 999,999 bells. Since it's gonna be 4.5M I'd say four worth 999,999 and one for 500K. I'll buy them and the next day the bells will appear in your bank. It just makes it faster than having to drop every bag.
I remember the general one being 100TBT for 6M IGB, and I say general because the threads that buy TBT or buy IGB, decide on it with the person they're trading with.