Pharmacy students are usually trained to use Stethoscope. But it is not always required. You might  need this during your anatomy classes and lab works specially. For practicing outside, you may also need this. But till your colleges doesn't ask you to buy one, you don't need to think about it much. If it the stethoscope is required for any kind of work, your college will ask you to buy one for that purpose. Then you should buy.