Does anyone know how to edit timthumb or style.css to cotrole thumbnail sizes?

All of my thumbnails are cut off at the top.
I tried many plugging but nothing helps.
If anyone knows how to fix this problem please help.
Please visit this thumb link to get a sense of my issue:
http://www.binarymoon.co.uk/demo/timthumb-basic/
Please rely only if you know how to edit WP style.css
Or the thimthumb code to resize the images appropriately.
My site is: http://amysbargain.com/testsite/
Thank you in advance!