There isn’t really any such thing as a „Latin font“. The ancient Romans only used majuscules (what we call capital letters), and they often did not leave spaces between words. On important documents and most monuments, however, words were separated by a punctuation mark called the interpunct (·). U’s were not distinguished from V’s, nor J’s from I’s. So this is what your tattoo would look like on a Roman monument:
SEMPER·TUA
But for modern use you may render it in minuscules (lowercase letters) with normal spaces(semper tua), as well as in any font that strikes your fancy(SeMpEr TuA.
Doesn’t really matter.