The typical multivitamin does very little for you, and many studies have shown that certain synthetic vitamins can in fact damage your heart and liver.
I eat healthy - only use smart balance for butter, olive oil for cooking oil and dressings, no bleached wheat products, don't drink soda, drink lots of green tea, and eat as many vegetables (and variety of) that I can.
If you want to take supplements, it's best to take an Ester-C complex (with bioflavanoids) and a natural Vitamin E complex with mixed Tocopherols.
Pills like "centrum" are mostly calcium carbonate, which has maybe a 5% digestion and absorption rate, and tend to pass through you like a rock. Plus the complex relationship of vitamins, minerals, and enzymes inhibits most of the absorption of various vitamins because you can't consume them together.