munge.rb

def deep_munge(hash)
  hash.each do |k, v|
    case v
    when Array
      v.grep(Hash) { |x| deep_munge(x) }
      v.compact!
      hash[k] = nil if v.empty?
    when Hash
      deep_munge(v)
    end
  end

  hash
end

params = {}
params["fees"]={"ranges"=>["100.0"], "values"=>["0.00"], "range0"=>"0.0"}
deep_munge(params)
# observe