Just to clarify the voucher system that Dunnes uses or at least my understanding of the T&C's
Dunnes offer lots of vouchers but the two main ones are the two "threshold" vouchers, a €5 off €25 and a€10 off €50
"Threshold" is the key word here, if you meet the "threshold" you get a voucher, spend €25 to €49.99 you get a €5 off,
€50 to €99.99 you get a €10 off, a €100 to €149.99 you get 2 €10 off's and €150 to €199.99 you get 3 €10 off's etc etc
The extra €5 off voucher you got when you spend €75, €125 or €175 is a "Top up" or "promotional" voucher and is time limited
So Dunnes can add or remove this at any time they wish, without giving us prior notice
You might remember a few years ago when you spent €50 at the weekend you got an extra €5 off without spending the €75