Tipping is not required, but highly recommended. The person who bags your groceries does not get paid, they are either too old or young to employ, so they rely solely on tips. The person at Costco that offers to help you to your vehicle also works for tips alone. The minimum wage in Mexico is only 173 pesos per day (roughly $8.65 US), so your tips can drastically change the lives of those who help you. Remember what seems to be a little change to you, means a lot to them.