In a conversation between a student and a banker telling her that there's an account for students which has "tasse d'interesse" can anyone tell me what's this?
Tasso (plural tassi) is the term we use to indicate a rate. Tasso di interesse is the rate of interest which, in your case, refers to the interest the student can earn by deposting money into the account the bank employee is proposing.
Not to be confused (but foreigners often confuse it) with:
Tassa (plural tasse) is the term we use to refer to tax/taxes, (an amount of) money paid to the government that is based on your income or the cost of goods or services you have bought.