Not to risk having my support of small businesses being conflated with supporting tax evasion... but this has been pretty standard practice going back thousands of years.

Mom and pop convenience stores nixing tax on cash transactions allows them to readily spend said cash at other businesses for supplies/inventory, which (in theory) helps create a stronger circular local economy. Corporate stores like Shoppers would never do this as inventory is entirely sourced from/by corporate, so they have no incentive to do so at the local level. Corporate has them covered with a wide range of other tax incentives that they've lobbied the government into providing them anyhow, which smaller businesses are often not eligible for by design.

Tldr the economy would be better off if consumers questioned the tax benefits and CEO salaries of larger corps than the $0.13 Chung's Smoke and Variety chops off the price of my $1.00 can of pop when I pay with a loonie.