38 CFR §21.156

1. (a)General. Other incidental goods and services may be authorized if the case manager determines them to be necessary to implement the veteran's rehabilitation plan. For example, a calculator may be authorized for a veteran pursuing an engineering degree, even though the veteran may not be required to have a calculator for any specific subject in his or her course, where there is substantial evidence that lack of a calculator places the veteran at a distinct disadvantage in successfully pursuing the course.
2. (b)Limitation on cost. The costs of incidental goods and services normally should not exceed five percent of training costs for any twelve-month period.