>> params = {"line_items"=>[{"quantity"=>"1", "sales_taxes"=>["11", "12"]}, {"quantity"=>"2", "sales_taxes"=>["22", "23"]}]}
=> {"line_items"=>[{"sales_taxes"=>["11", "12"], "quantity"=>"1"}, {"sales_taxes"=>["22", "23"], "quantity"=>"2"}]}

>> query = CGI::unescape(params.to_query)
=> "line_items[][quantity]=1&line_items[][sales_taxes][]=11&line_items[][sales_taxes][]=12&line_items[][quantity]=2&line_items[][sales_taxes][]=22&line_items[][sales_taxes][]=23"

>> parsed_params = ActionController::AbstractRequest.parse_query_parameters(query)
=> {"line_items"=>[{"quantity"=>"1", "sales_taxes"=>[]}, {"quantity"=>"2", "sales_taxes"=>["12"]}, {"sales_taxes"=>["22"]}, {"sales_taxes"=>["23"]}]}

>> params == parsed_params 
=> false # check out how much different they are