I'm looking for a Science Fiction story that takes place far in the
future, after the the earth has almost been destroyed by nuclear war. 
People live underground and worship a scrap of paper with
indecipherable writing on it. Subsequently a "Rosetta Stone" of some
sort is found that enables the  writing to be interpreted. It turns
out is is a shopping list with something like,"Bring home a Rye Beard"
 and other mudane items listed.   The answer will include the title of
the story, the author and where it can be found in publication.

Hi bstuttman,

I'm sure you are looking for "A Canticle for Leibowitz",  by Walter M. Miller.

"A Canticle for Leibowitz",  by Walter M. Miller.
"...In moving this rock, Francis discovers the entrance to an ancient
fallout shelter containing "relics", such as handwritten notes on
crumbling memo pads bearing cryptic texts like 'pound pastrami, can
kraut, six bagels?bring home for Emma'..."
http://encyclopedia.thefreedictionary.com/A%20Canticle%20for%20Leibowitz

Study Guide for Walter M. Miller, Jr.: A Canticle for Leibowitz (1959):
"Although A Canticle for Leibowitz was published as a book in 1959,
one version of it was written earlier. The first section, also
entitled "A Canticle for Leibowitz" (now "Fiat Homo" ["Let There Be
Man"]) appeared in 1955, the second section appeared as "And the Light
Is Risen" ("Fiat Lux" ["Let There be Light"]) the next year, and the
conclusion appeared in 1957 as "The Last Canticle" ("Fiat Voluntas
Tua" ["Thy Will Be Done"]), all in The Magazine of Fantasy and Science
Fiction. When he reworked the material for the novel, Miller made
substantial changes and additions. Although he published a few stories
before and after, and wrote most of a sequel to Canticle, at his death
this remained his only successful work. The sequel, Saint Leibowitz
and the Wild Horse Woman was almost finished when he committed
suicide, and was completed by Terry Bisson and published in 1997.
Canticle is widely considered a classic, has never been out of print,
and is widely taught in science fiction courses."
http://www.wsu.edu:8080/~brians/science_fiction/canticle.html

There are many used copies available, you can see a list here:
http://www.bookfinder.com/search/?author=&title=A+Canticle+for+Leibowitz&submit=Begin+Search&new_used=*&world_english=on&binding=*&isbn=&keywords=&minprice=&maxprice=&classic=on&currency=USD&mode=advanced&st=sr&ac=qr

Amazon:
"Walter M. Miller's acclaimed SF classic A Canticle for Leibowitz
opens with the accidental excavation of a holy artifact: a creased,
brittle memo scrawled by the hand of the blessed Saint Leibowitz, that
reads: "Pound pastrami, can kraut, six bagels--bring home for Emma."
To the Brothers of Saint Leibowitz, this sacred shopping list penned
by an obscure, 20th-century engineer is a symbol of hope from the
distant past, from before the Simplification, the fiery atomic
holocaust that plunged the earth into darkness and ignorance."
http://www.amazon.com/exec/obidos/tg/detail/-/0553379267/104-6427078-9815909?v=glance

I was happy to have found this for you. If you have any questions, or
if this isn't the title you are looking for, please post a
clarification request before closing/rating my answer and I'll be
happy to reply.

Thank you,
hummer

Google Search Terms Used:  scifi post nuclear war "shopping list"

Terrific!  Exactly what I was looking for.