How can i change Tax Rate Decimal Places to 0 Zero

Dear All
i wanna change all number without decimal . How can i do that without any change in sql
just add 0 to Tax Rate Decimal Places in setting??
my currency didn’t need any decimal number.
also in my country fist day of a week is Saturday how can i add this to my setting

  • i wanna ask how can i add Jalali Date Time instead this time??