This question already has an answer here:
- Why we put 'A' after each Hindu name? 3 answers
As already discussed here: Why we put 'A' after each Hindu name?, the subsequent "a" in an English transliteration word, is to interpret the Sanskrit word for full pronunciation.
- RAma (राम) is neither RAmA (रामा) nor RAm (राम्)
- Krushna (कृष्ण) is not KrushnA (कृष्णा)
- Atma (आत्म) is not AtmA (आत्मा)
Similarly, Is it "भगवद्गीता" or "भगवद्गीत"?
Note: Though in the popular culture including wikipedia, it seems the 1st one, hardly it's spelled with last word as "A" or "ā".