should just allow all participating stalls/shops to issue balance in cash? Eg chui use voucher to buy $7 of food, use $10 CDC Voucher would get $3 change in cash no questions asked!
i went a few places, the stall owner, and mostly are owners, usually okay to give cash change back.
tbh i feel one or two dollar is not a big issue especially since the denominations are fixed. Only like if you try to exchange $100 for cash without buying, then that is illegal la. Also, if the stall owner don't want give change, then don't force them because by right cannot.
Remember SAF 8th rule still applies.