Spaniards still have not fully got to grips with the value of the euro and often tip too much, according to Economy Minister Pedro Solbes.
Over-tipping had added to the sense among Spanish consumers that the cost of living is higher since the euro's introduction in 2002, he said.
"People haven't taken on board the value of a euro," Mr Solbes told a political rally in Madrid.
Spain's inflation is higher than other eurozone states - at 4.1% last month.
"I see people having a couple of coffees and calmly leaving a euro tip," Mr Solbes told a Socialist Party economic forum in the Spanish capital.
"That's 50% of the value of the product."
Before the euro hit the streets five years ago, leaving a 25 peseta tip was the norm. One euro was then worth 166 pesetas.