Plasterboard tape required?

[daveok77]

Hi all. I'm doing up a bathroom as a DIY project. Going to tile all the walls, including shower enclosure all the way up to ceiling. Is it necessary to tape all of the plasterboard joints prior to tiling? Was looking at the tape itself from Mapei and comes up around £5 per metre which seems extortionate. Just wondering whether the joints can be filled with something else like adhesive or a gap filler? Thanks.