If the wine is "corked" you can (and should) reject it.
If the wine clearly doesn't match the description on the wine list (e.g. it's a red wine which is described as 'subtle' but it turns out to be 'full-bodied') it's not 'fit for purpose' and you can reject it.
If the wine is in good condition and 'as described' you've entered into a contract to pay for it.
the tasting isn't to decide whether you like it or not, its a hangover from the days when more bottles were "corked" and not drinkable. While I don't disagree with Chris' comment about wines not being as described, IMO opinions on wine are very personal things for most of us and unless the difference was a gross one (still instead of sparkling, red instead of rose) i think you'd have a hard job rejecting it.