dont think just because you are innocent the IRS wont make you miserable or will not believe you are guilty of not paying all taxes.
IRS agents have to justify their time spent. They have bosses they report to like anyone else. They have to produce, like any other job holder. If their are too many cases assigned to them where they go back to their boss and say "Yeah I spent 240 hours investigating this guy, but turns out he did pay all of his taxes", that is 240 salaried hours they spent to generate zero income. that is bad for them and their career at the IRS.
your chances of audit do skyrocket. you "should" be OK if you pay all taxes. just dont believe you WILL be OK with the IRS, because you may not.
you send documentation of all wagers/deposits/etc, they think their are probably more and winnings you are omitting.
you somehow prove thats not true ( I dont think anyone can) and they will come after you for something else.
you got any Vegas winnings you didnt declare ( not saying you do, but they will start hunting elsewhere and elsewhere on your return)
bottom line-they dont like to spend a lot of time on an audit to come up empty handed.
know the risks if you are going to do this