Yes, you can get a .com domain registered in Rs. 99 with Bigrock or Godaddy. The offer price Rs.99 is for first year only after that they charge you Rs. 689/year for the renewal of your domain. To get domain in Rs. 99 from Godaddy, follow the following instructions:
1. Go to the site https://in.godaddy.com/deals2/default.aspx?gclid=CjwKEAjwla2tBRDY7YK9uKXe8R8SJAAhG6LGlevX2P77KQknNza0JpVml1Gx_85gb9d0nFdN-TV1ORoCT5jw_wcB&isc=goflin11¤cytype=INR&cvosrc=ppc.google.godaddy+99+rs+domain&cvo_crid=75560456686&matchtype=e&ef_id=VathtAAAAZwebdNV%3A20150719084155%3As
The above link may not work, so copy and paste it in your browser's address bar.
2. Search for your domain and add to the cart. Don't worry about the price shown. The price shown will be 199.
3. Do not take any offer and click continue to Cart. Then Proceed to Checkout.
4. Your promocode goflin11 will be automatically applied and the price will be shown 111 including ICANN fees.
4. Pay the amount through net banking or credit card.
That's it now you have purchased a .com domain in 99 rupees.