There were 181.77 million of these minted in San Francisco (S) that year and depending on amount of wear and collector demand it may be worth about .05 to maybe $1 or more.
The 1945-D cent is a common cent, it had a mintage of 226,268,000. The D is indeed for the Denver mint. The coinage of the USA as well as most of the world was minted in huge masses due to World war II. Few coins from this period are rare or even scarce. One can find the 1944-D cent in a coin dealers wheat cent box for from .02 to .05 cents. It will be many years before it's value goes up. Your coin has more of a historic value than a monetary one.
The value for a 1945 copper penny currently stands at around 4 dollars. However, it should be noted that different coin traders offer different prices for different coins. For more information on the prices of the different coins visit: http://www.coinflation.com.