First, these laws are generally pretty flexible. They account for cost increased during emergencies. Also, grocery costs vary anyway and so the "base" price can be higher than normal supermarket prices.

Second, labour costs are not 100% of a supermarket's costs, so a 10% increase covers a lot of extra labour. Considering the sheer volume of sales they're doing, it might actually pay for that %200-%300 wage increase... though you don't actually need it to go that high.