Poor old Zaccheus just couldn't help himself to a bit of money on the side even though he was paid well to collect taxes for the loathed Roman occupying force. Read the story direct from the Bible:
Jesus and Zaccheus
Jesus entered Jericho and was passing through it. A man was there named Zacchaeus; he was a chief tax-collector and was rich. He was trying to see who Jesus was, but on account of the crowd he could not, because he was short in stature.
So he ran ahead and climbed a sycomore tree to see him, because he was going to pass that way. When Jesus came to the place, he looked up and said to him, ‘Zacchaeus, hurry and come down; for I must stay at your house today.’
So he hurried down and was happy to welcome him. All who saw it began to grumble and said, ‘He has gone to be the guest of one who is a sinner.’
Zacchaeus stood there and said to the Lord, ‘Look, half of my possessions, Lord, I will give to the poor; and if I have defrauded anyone of anything, I will pay back four times as much.’
Then Jesus said to him, ‘Today salvation has come to this house, because he too is a son of Abraham. For the Son of Man came to seek out and to save the lost.’
Source: http://bible.oremus.org/