Cal. Rev. & Tax. Code § 19256

The Franchise Tax Board may, in the allowance of any amount as a credit or refund, or in the collection of any amount as a deficiency or underpayment, of any tax imposed by Part 10 (commencing with Section 17001) or Part 11 (commencing with Section 23001), disregard a fractional part of a dollar unless it amounts to fifty cents ($0.50) or more, in which case it shall be increased to one dollar ($1).