If you have interest in Law and Taxation, in the industry you cannot get a job which will enable you to work in both departments simultaneously. Therefore I would suggest you to choose one of them and do courses based on it.
One area where taxation and law can be combined are the Indirect Taxes. You can do DTL course and get job in tax department as well think of doing your own practice as a Tax Consultant.
Bank PO are very different than what you are thinking of. They are not particularly related to law and taxation. An LLB and DTL will be a fantastic combination for you.
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