Change the tax rate on calculator on MS-8TV

SETTING YOUR TAX RATE
you hold your set % button down for three seconds until set shows again, then hit tax rate button it shows your tax rate, change your tax rate then hit set your tax rate should be set.



cliff notes:
hold set% button
hit tax+ button
change the desired % 
hit set done


Do rate the solution.

I already set my tax rate.for tax+ the amount is correct but for tax- it isn't.ex: tax- (2%) from 7200000=7058823 and for tax+ (2%) from 7200000=7344000.Help Please