Because people pronounce things differently, there are no “official rules” for transliterating Hebrew letters and words into the English alphabet. Because there are various transliteration schemes, often you will find different transliterations (and hear different pronunciations) for the same Hebrew word!
For example, Ashkenazi (German and eastern European) pronunciations common in English-speaking countries often shift “a” sounds towards “o,” turn some “t’s” into “s’s,” and accent the next-to-last syllable whereas Israelis accent the last syllable. For example, Ashkenaz say “Shab•bos” instead of “Shab•bat”; “Mo•shi•ach” instead of “Ma•shi•ach”; and “Tal•lis” instead of “Tal•lit”.
On this web site, transliterations will use dots (or sometimes hyphens) to separate syllables and the accented syllable will be shown in boldface. For example: