I have five locks on my house with five different keys.  I would like them changed and keyed alike.  Is that possible?

Yes.  Your professional locksmith can key locks alike if they are the same manufacturer's brand.  If they are not the same brand, there is a possibility that they may still be keyed alike if a key blank can be found that will enter into all the locks.  It is not the best way to accomplish the task, but it will sometimes work.  The proper way is to replace the one or two locks that are not the same and then use the original manufacturer's key blanks in the lock.