Cal. Rev. & Tax. Code § 18623

(a) The Franchise Tax Board is authorized to provide, with respect to any amount required to be shown on any return, form, statement, or other document required to be filed with the Franchise Tax Board, that if the amount of the item is other than a whole dollar amount, either of the following shall apply:
1. (1) The fractional part of a dollar shall be disregarded.
2. (2) The fractional part of a dollar shall be disregarded unless it amounts to one-half dollar ($0.50) or more, in which case the amount (determined without regard to the fractional part of a dollar) shall be increased by one dollar ($1).
(b) Any person making a return, statement, or other document shall be allowed, under regulations prescribed by the Franchise Tax Board, to make the return, statement, or other document without regard to subdivision (a).
(c) Subdivisions (a) and (b) shall not be applicable to items which must be taken into account in making the computations necessary to determine the amount required to be shown on a form, but shall be applicable only to the final amount.