SHEBOYGAN, Wis. (WHBL) - A Sheboygan man who was cashing fraudulent checks to finance his heroin habit has been sentenced to prison.  22 year old Miguel Diaz had cashed six checks for more than three thousand dollars at a Sheboygan convenience store last September.  During the investigation he was identified - through surveillance video - cashing the checks that had been made to look like payroll checks from a local temporary staffing agency.  Diaz was sentenced this week by Judge L. Edward Stengel to two and a half years in prison to be followed by 3 years on extended supervision.  A Sheboygan man and a Milwaukee woman also involved in the check cashing scheme were in court last month and placed on probation.