It's worth around $2 in uncirculated condition; otherwise it's only worth face value. Five cents.
The value of a 1940 United States nickel varies depending on its condition and any unique characteristics it may have, such as mint marks or errors. In general, a 1940 nickel in average circulated condition is worth around 50 cents to a few dollars, while one in uncirculated condition could be worth $10 or more.
In circulated condition, no added value 1940 Jefferson Nickel; With no mint mark, in very fine condition is worth $0.20, uncirculated is worth $1.75, proof is worth $37.50. With D mint mark, in very fine condition is worth $0.25, uncirculated is worth $3.75. With S mint mark, in very fine condition is worth $0.30, uncirculated is worth $3.50.
The coins are still found in circulation, so if it's not a uncirculated coin, it's only face value.
It's the usual practice of this site to answer a single question at a time. Please see:"What is the value of a 1940 US nickel?""What is the value of a 1942 US nickel?""What is the value of a 1944 US nickel?"
A 1957 nickel is worth face value only, unless it's uncirculated or a proof coin.
If it's not uncirculated, just spend it.
Liberty Nickels were made from 1883-1912, a Jefferson nickel dated 1940 is still found in circulation, a uncirculated coin may be worth 50 cents.
Unless it's proof or uncirculated, 5 cents. It's a Jefferson nickel not a Monticello nickel.
Your coin is called a Jefferson nickel. Liberty nickels were minted from 1883 to 1912. For information on values and mint marks please see the question "What is the value of a 1940 US nickel?"
Still only 5 cents.
Unless it is uncirculated, it's pocket change.