What is a 2000 5 pence coin worth?

To clear things up, modern "eagle" coins aren't related to the old eagle denomination ($10) in use until 1933. The name is now applied to all silver and gold bullion coins sold by the US Mint. For legal reasons they all have artificial denominations but they're sold by weight so their value is determined by the price of their precious metal(s). There are modern eagle coins with artificial denominations of $5, $10, $25, and $50. None are made with a value of $20 which would have corresponded to the pre-1933 double eagle coin.

Assuming you have a "$25" coin, it contains 0.5 troy oz. of gold. Its retail value would be essentially the same as half the spot price of gold, which changes every day.

NOTE: The only U.S. gold coin to have a $20 denomination since 1933 is the 2009 Ultra High Relief gold coin. This coin was produced in 2009 basically to show the advances in minting techniques of the U.S. Mint. All were struck as uncirculated coins at the West Point Mint. It's a modern version of the "1907 Ultra High Relief" double eagle coins, hence the $20.00 denomination. They contain one ounce of 24-karat gold and are 4-mm thick. Average market values are $1,450.00-$1,500.00 depending on the grade of the coin.