Hi,
my english teacher (she was from the uk) taught us to avoid "sincerely yours" and to use only "yours sincerely", because "sincerely yours" sounded too much like "all yours"...
'Yours sincerely' is the standard and polite way of ending a letter. The words mean very little.
'Sincerely yours' sounds warmer, more friendly, more personal. You can use it whan you are writing to a friend.
[ Please remember that capital letters are an important part of good English. The sentence you posted has no capitals at all, so it will be incorrect in an exam. ]
Best wishes, Clive