"We calculate that the increase was driven almost entirely by volumes - a consistent and notable development over the last year, and one that is likely to coincide with a pickup in general economic activity," said Westpac economist Michael Gordon.
Spending on consumables, which include food, rebounded, rising 1.1 per cent after falling 1.6 per cent in April.
For the third month in a row the hospitality sector enjoyed a notable rise in sales, up 1.6 per cent for the month and 7.9 per cent for the year.
"Spending in this category has been boosted this year by higher consumer confidence and strong overseas visitor numbers," said ASB economist Daniel Smith.
Spending on durables, such as furniture and appliances, slipped 0.4 per cent but that followed a very strong 3.3 per cent rise in April and it is still 7.9 per cent up on May last year.
Smith said high spending on durables was supported by increased housing market activity and was another sign of consumer confidence.
Confidence had improved late last year and early this year and that had coincided with a turnaround in net migration flows, he said.
"Further increases in house prices have the potential to spur greater growth in consumption, but the available evidence suggests that households retain some caution, possibly a symptom of high household debt levels and a relatively soft labour market," Smith said.
Deutsche Bank chief economist Darren Gibbs said that for now consumer spending, as reflected in card transactions, was growing broadly in line with labour incomes, as measured by the Quarterly Employment Survey, and less enthusiastically than might have been expected given the rapid rise in house prices, especially in Auckland.
"The Reserve Bank will be hoping that this remains the case over coming months," Gibbs said.
Smith said that despite steady growth in retail sales, consumer price inflation had been very subdued over the past few years, in large part because of the strong Kiwi dollar.
"While the currency has backed off from its recent highs, we do expect it to remain reasonably high by historical standards over the next 12 months."
He said retail inflation was therefore likely to remain low.