If people are only occasionally typing in "/troussers" instead of "/trousers" then let it 404. Its there to let people know "I'm sorry, this isn't here. Perhaps you misspelled something." You could always 301 it if you really felt like it because it wouldn't hurt anything in the long run.
Now, if you found that you're sending 500 people a day to a 404 page for "/troussers" when they're looking for "/trousers" and you find there are relevant inlinks pointing at the wrong page then by all means go and 301 those people to the correct page. They'll be better served by it. But if you're redirecting all of those people to "All Categories" then you aren't being thoughtful of the customer's needs.
Indiscriminately 301ing everyone to "All Categories" without considering what their intentions are is not helping that customer and will likely wind up with an ever increasing bounce rate on "All Categories".