A key measure of inflation fell to nearly a five-year low last month as apartment rental price growth slowed and gas prices fell, offering some relief to Americans still grappling with the sharp increase in costs of the past five years. Friday’s report suggests inflation could be cooling, but it comes after the cost of food, gas, and apartment rents have soared since the pandemic, with consumer prices about 25% higher than they were five years ago. The increase in such a broad range of costs has become a high-profile political issue under the rubric of “affordability.”