This is how it works:
There is only one check made. The PC's Appraise skill.
The procentage gained is a 5th of your Appraise skill, meaning your Appraise skill divided by 5.
The maximum procentage is then 9%. (43/5=8,6~9.0)
Only base skillpoints apply, meaning the actually skill points you placed out at level up. Items or Spells will not help you.
No Dice Roll involved, so no need to Open/Close the store to try to get a better roll.