If they emigrated in 1888, they should both be in the 1880 Swedish census, which you can search at riksarkivet.se Anna was probably Anna Andersdotter or Anna Andersson, and Claus Johnson would probably have been Claes Johansson or Klaes Johansson. Since his is the more unusual name, he is probably easier to find, unless you know her middle name. How certain are you of their birth years?
Also note that if they were from the city of Borås, their birth records may be listed in one of the Borås city parishes but there are also a few surrounding parishes e.g. Torpa, which could apply in the years they were born, since the parish borders have moved around a bit and parishes have been incorporated into another. -Elisa