First, you can retrieve information about current autogrowth parameter in sys.database_files
if is_percent_growth = 1 or growth <> 655360 (it means 655360 pages of 8 kb = 655360 * 8 \ 1024 Mb = 5 Gb)
change it with
ALTER DATABASE [YourDb] MODIFY FILE ( NAME = N'your_file_name', FILEGROWTH = 5Gb )
GO
your_file_name come from sys.database_files as well
use type or type_desc to check if you're dealing with log or data file