Catalysis of the reaction: a cytidine in tRNA + S-adenosyl-L-methionine = a 5-methylcytidine in tRNA + S-adenosyl-L-homocysteine + H+. This modification can occur on seversal residues, including cytidine(34), cytidine(40), cytidine(48), and cytidine(49).
tRNA (cytosine-5-)-methyltransferase activity