A cash register's drawer can only be opened by an instruction from the cash register except when using special keys, generally held by the owner and some employees (e.g. manager). This reduces the amount of contact most employees have with cash and other valuables.
Internal medicine or general medicine (in Commonwealth nations) is the medical specialty dealing with the prevention, diagnosis, and treatment of adult diseases. Physicians specializing in internal medicine are called internists, or physicians (without a modifier) in Commonwealth nations. Internists are skilled in the management of patients who have undifferentiated or multi-system disease processes.
They do procedures that cost more, and there are fewer of them. Internal medicine doctors are general practitioners. You can also go on to specialize from an internal medicine background by doing fellowships in things like GI or pulmonology or nephrology or cardiology after you complete a medicine residency. Specialists in those fields make more, usually, than GPs.