Assuming all bills and no coins: If the envelope contains an odd amount of money, swap it.
I still trade in the stock market. but only ETF or Exchange Traded Funds that go long or short using signals from a system called ETFBULL..their website name is the same.
They have great historical performance, they give bullish and bearish signals for all the indices and are right on the money.
They recently closed a bunch of long positions with an excellent profit for my account and reversed to bear positions that are starting to perform. I find their market direction prediction nothing short of amazing.