It has a 1/3/7/35 Pass overwrite option, 3 pass by default but 1 pass is enough, the more 'passes' the longer it takes too.
1 pass is most often always enough though
Personally i use CCleaner alot as a 'disk cleaner' / junk/history cleaner but reserve a program on bootable usb disk to wipe physical disks which i would connect through a hot swappable caddy/enclosure