There is big money in pocket change. A new $105 million fundraising round for Acorns Grow Inc., whose namesake smartphone app automatically invests small contributions from users into baskets of stocks and bonds, values the startup at $860 million, the company said Monday. That is more than triple the valuation Acorns attained in a 2016 financing round, and it makes the startup worth more than robo-adviser rivals including Betterment LLC that have raised more capital from investors and manage several billion dollars more in client assets.