"'Amazon Not-too-bad' store" sounds pretty reasonable. Maybe a too-clever work around for the 5-Star problem would be to call it "100-Star," which would be 4 in binary notation. Or they could call it "5th-Star" since 4 stars is the fifth number of stars b/c the range of starts is zero indexed.

  Ordinal : Cardinal
  1 : 0
  2 : 1
  3 : 2
  4 : 3
  5 : 4
  6 : 5