A blank planchet for a nickel is worth about $2.00
The mint mark on a cent, if it has one, is always below the date. Private companies often stamp special symbols onto cents (e.g. JFK's picture, a logo, etc.) and sell them as novelties, so my guess is that is what you have. It has no numismatic value and is worth only face value.
You could spend years looking through bank rolls and never find anything worth more than a buck or two. There simply have been too many people searching those coins, and anything worth anything has already been plucked out. You would have to get lucky and catch some rolls that somebody (like a little old lady) has brought out from some stash and taken to the bank.
Less than 11% of all the 1957 series Silver Certificates have the star by the serial no. If your Silver Certificate is in choice crisp condition it is worth $40.00. In circulated condition, it's worth about $5.00