Is been 25 years since I took Japanese in highschool but I'm relatively certain that our textbooks had ち romanized as tchi which from my recollection seems more accurate to its actual common pronunciation.
Perhaps only in the case where it's preceded by the small tsu? E.g. "一人ぼっち" -> "hitori bo[tsu]chi" -> "hitori botchi"? That's what Wikipedia says [1], although I think it's also common to (incorrectly?) use "bocchi" instead.
