Illustration: Eniola Odetunde/AxiosKilling the penny could trigger a small "rounding tax" that forces cash-paying consumers to spend a bit more at the register, according to a new report from the Federal Reserve Bank of Richmond.Why it matters: With the one-cent coin's upcoming demise, making sense of cents — and getting exact change — could get a lot trickier.Getting rid of the penny could disproportionately affect low-income and older Americans, who are more likely to use cash.The big picture:...