I don't think it'd be a particularly popular decision to use tax dollars to pay for a murderer to have a funeral celebration and burial. Maybe that's callous but I'd guess that's the way it is in the US.

As far as I know it's up to relatives or loved ones to bury their deceased and its up to them to arrange a funeral, plot of land, headstone, etc which runs in the thousands of dollars. If there is no one willing or able to pay then I'd assume the state essentially disposes of the body by cremation.