Acorns is a simple savings and investment app that rounds up your credit or debit card purchases to the nearest dollar and invests it.

Contributor CJ Reid accepts roundups of less than $0.50, "like my $3.60 cup of coffee."

"Rounding up 40 cents here and 25 cents there moves me swiftly enough to $5 so that I can begin investing without putting myself into the red," she says.

Once your round ups reach $5, the amount is transferred into your Acorns account and invested into your chosen portfolio.