This article argues that clever pricing strategies and the ability to cut transaction fees payments less than $1 may help speed the adoption of cryptocurrencies.

https://cryptostar.money/blog/britain-is-keeping-the-penny-lessons-for-crypto-marketing-teams/

--- update 15:33 ---

Great points Beerwizard and Stompix  below.

When using crypto the buyer pays the transaction fee. Cash is cheaper for them unless they get a discount.
Merchants using Lightning Network might have to close their channel each night to keep their books in order.