Prices are going to be in KSh -- the local currency (Kenyan shillings). Usually, at checkout the final total from the register/terminal is entered into whatever bitcoin merchant payments/wallet is used (e.g., Blink wallet), which converts to sats and an LN invoice is produced. https://www.blink.sv/en/merchant-tools

If this is done with just a bitcoin wallet (e.g., Wallet of Satoshi, or Machankura), then the merchant converts, using an exchange rate app, first to USD and then to sats. The buyer then sends to the merchants Lightning Address, or scans a QR code (e.g., zero-value LN Invoice, or scans the QR generated for the transaction from the merchant's wallet).