The currency of India is the Indian Rupee.
Although ATM machines are available in the big cities and some towns near Balipara it is advisable not to rely on them.
You can change major foreign currencies like US Dollars, Euros and British Pounds at the HDFC Bank and The State Bank of India in Tezpur on production of the original Indian entry stamp on your visa in your passport.
Please check for the latest exchange rates before travelling.
Bargaining at the market and in non-fixed price shops is a common practice.