How STT is applied in Options

Today is Nifty expiry and many traders will indulge in Option trading to make some quick buck if they are on right side of trade. I have seen trader taking position in Options that trades less them their theoretical value, thinking price will correct End of day and they will make profits but in reality end up making losses Many traders every expiry do not  sell their ITM options and letting it expire(especially which are very close to strike price) or else take trades/strategies assuming that discounted price of option will correct before the end of the expiry day.
Let me explain them with few elaborative examples:
1. Nifty is trading at 5650 and today is the day of expiry. At around 2:00 PM, Nifty 5600 calls and 5700 puts are trading at around Rs 45. Ideally it should be at least 50, so why?
The 5 rs difference in price in above scenario is because of  Security Transaction Tax or STT. Exchange applies STT as discussed below.

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