At the risk of stereotyping: you live in Florida where there are a lot of retirees. You might not see it as often because they tend to penny pinch more, but get to where there aren't a large number of elderly and you see more people throwing pennies away than you see saving them. And by throwing away I mean that I have actually seen them go in the garbage.
No, they're quite common on the ground here. I won't stop the parade (so to speak) to pick one up, but if I'm bending down tying my shoe, or just waiting around, I'll pick it up. I won't pick one out of a trash can or ashtray, but you get the idea. I think it's careless to throw out money, personally. I mean, it is worth something, however minuscule.
Some people just like to show off, as if tossing out 4 cents makes them look important. Call me cheap, but it's still money. Besides, I dislike having tons of loose change, so a penny here in my coin holder now in the car makes correct change later.
In any case, I don't think the penny is going extinct. Plenty to go around, no real reason to hoard it. People just like to hoard lots of worthless things, because they think everything is collectible. Even if the value of a penny's metals were worth, say... 1.5 cents, nobody's going to go around and offer more than face value for somebody's penny collection, since it would cost too much to melt them down. The copper component of a penny minted in the past 10-15 years is about 1-2%, and the rest is zinc. Surely a cheaper metal exists, like aluminum.
From my experience in Spain, the one peseta coin was rarely used, and people tended to round one way or the other, if needed. Most items didn't have sales tax, and items were sold in increments of 5 pesetas, anyhow. The exception was the fresh food market, where individual items were of such a small value, that the smallest possible unit of money was a bit more practical.
With most states in the US charging some percentage of sales tax, it's rare to see prices come to some exact price, especially when many items or services are sold with $x.99, $x.49 or $.95 at the end (you'd figure that old process would finally disappear by now), so the penny is hard to kill off. Also, try to convince people that they should always round up; it would be similar to another tax to some people, to expect another 1-4 cents.
In any case, if the "round up" technique were used, I believe that in 10 years, nobody would question it any further and the penny wouldn't be missed. I say this because with every sale tax increase, people stop complaining after a year's time. If the penny's production were to be halted, the US Mint could force the hand, and if the supply of pennies dried up, then people and businesses would have to comply. The argument the Federal Reserve could say is, "Well, there's enough for every man woman and child in the US to own about 100 of them."
