Is it permissible for an employee to accept money from those whose transactions he completes without request or insinuation, and is that considered a bribe, especially given the fatwa of some allowing it as charity for the poor employee?

The gifts given to an employee for performing work for which he receives a salary are unlawful (haram (definition)), considered ill-gotten gain (suht) and embezzlement (ghulul). They are deemed a bribe, even if not requested. The Prophet, peace and blessings be upon him, clarified that if the employee had stayed in his parents' home, he would not have received such gifts, which confirms that they are a bribe and not a gift or charity. Lawful wealth is blessed, and a small amount of it is better than a large amount of unlawful wealth.