Swish is 1 to 2 SEK (2 being the list price that can be negotiated) per transaction. Then swish has a daily cap of payments you as user can do of 150k SEK (system limit, not a soft cap that the user can remove).
That is an extremely low limit for any noteworthy business, equating to $500k USD a month total. Most small grocers here in Seattle do more than that in credit/debit monthly.
The Swish limit is for outbound payments, not total transactions.
So a grocer that accepts Swish payments will in no way be hindered by this limit, unless they for some ungodly reason are also swishing money back to customers.