Bolt, a startup that offers online checkout technology to retailers, announced this morning that it has added $75 million to its Series C round, bringing the financing to a total of $125 million. WestCap and General Atlantic led the new tranche, which Bolt CEO Ryan Breslow told TechCrunch was raised at around twice its Series C valuation. PitchBook pegs the company’s Series C at a post-money valuation of $500 million, implying that the Series C1 values Bolt at around $1 billi