Customize Unicenta POS

Hello, I am looking to customize Unicenta POS for my small business.
1) Looking to add static buttons on the page that do not move away (example - Grocery)
So, if someone purchase some grocery I can punch in the amount and hit Grocery so at the end of the day when
I print report it gives me the amount of grocery sold.
2) State tax calculation (9%) and additional tax ($0.05 per can or glass bottle based upon the volume i.e. 24oz or 32oz or a pint) also based upon the quantity purchased. (example - one can of Pepsi or 6 pack)
3) Have a static service charge button for selective transactions.
4) Top selling items reoort
5) Daily or on demand inventory report
Please send in bids (I am a new business owner tyring to keep costs to minimum or none, I am willing to test with you)
Thank you