Below is a statemenet issued by the The Central Bank of Kenya (CBK), which was published on  2nd October 2015;

The Central Bank of Kenya (CBK) has noted with concern that some supermarkets issue airtime, matchboxes and sweets in lieu of currency coins without affording the customer the option to first obtain change in currency coins. The Central Bank of Kenya would like to clarify that:
1. There is an adequate stock of coins and the Central Bank of Kenya has
issued commercial banks with sufficient quantities of Kenya currency coins to
facilitate smooth settlement of transactions.
2. The law requires that all monetary obligations or transactions entered into or
made in Kenya be settled, in Kenya currency unless otherwise provided for by
law or agreed upon between the parties. It is therefore a violation of the law
to deny customers the possibility of obtaining their change in Kenya currency
or deny them the opportunity to agree to settle the transaction in any other
form.
3. Commercial banks, supermarkets and other entities should desist from the
practice of issuing alternative products instead of currency coins on the basis
of bulkiness or perceived shortage. Accordingly, Central Bank of Kenya urges
commercial banks to ensure that coins are re-circulated efficiently at all times
to their respective customers.
4. Any member of the public experiencing difficulty using coins as a means of
exchange or in depositing with commercial banks, is urged to contact any
Branch or Currency Centre of the Central Bank of Kenya for assistance.

Source: Central Bank of Kenya press