With b.com what course should i do to learn taxation

Hello seniors, This is sonia gupta. i am pursuing my b.com final year, having an experience of approx 4 & half years in general accounting. i wants to learn about taxation i.e.,return filling,sales tax,exice and all. could any one suggest me what course should i do? to get a good job and to learn about taxation. please help me out. sonia gupta