A good way to bury things is to get large PVC pipe and the end fittings and make a secure tube. Use the plumbers glue to secure the fittings over the ends as you would for plumbing for long term burial. For short term storage of items you need to get to just thread one or both ends for the screw caps that are used for vent caps and use plumbers tape.
Yes the sealed pipe might work, but it could also sweat and that will cause a roll of bills to form a clump of fibers.
LOL, never bury pennies in a jar, it broke somehow and for years afterwards, we found pennies in that spot.
That will be good for us, as when you find a penny, it means your Guardian Angel is on guard duty and threw it down, so you would know.
That is a very old Hungarian folk story and it pleases me, I always look up and thank God for all the guarding that he has ordered for me all these years.