The tax collection system of first century Rome involved the use of collection agents who were assigned specific regions and given targets for how much they needed to collect. They were granted authority (and usually a few goons) to go around and collect taxes from everyone. The tax collector was liable for the full amount, so whatever he couldn’t collect from his region came out of his own pocket. Consequently, they usually collected more than they needed and pocketed the rest. The moneys collected took food from the mouths of children and generally went straight into the maw of the army. Few imperial areas really liked the tax collectors, but in Judea, tax collectors were liable to be beaten or killed.
Upper class Romans would eat while reclining on a long couch, allowing servants to bring and remove dishes from a nearby table around which other wealthy Romans would be lounging. There would be a lot of talking, a lot of drinking, and eating together like this was a fundamental and cherished element of Roman society. If you were at the top of the upper class, you would eat with the very wealthiest in your environs. Those whom you ate with helped to define your position on the social ladder. Those who would host such events could easily become like local kings.
Mark 2:15 is not about the gang catching the value menu at a Wendy’s. It’s not about how Jesus was snacking with burglars and hookers. This is not a bread line or a soup kitchen. This is Jesus, in his own house, hosting a fancy meal with the wealthiest, best-connected people in the region. Not just a couple, either: many people were there – many people followed him.