The Postal Service uses no tax money to operate, since the reorganization in 1970. Although it is going broke.
...and they're requesting a bajillion dollar bailout.
There are dozens of different boxes showing up at my house every year, from various things we order. Heck, clean out your plastic mayonnaise or peanut butter jars. Those make GREAT ammo containers for pistol rounds. That is, unless you're one of those confused folks who happens to believe that old myth about the rim or nose of one round rubbing against the primer of another, setting it off.