Baby clothes have been listed as essential items that should go on sale in supermarkets during Wales' lockdown.
The Welsh Government has also said customers should be able to ask for non-essential items in exceptional circumstances.
But ministers say the principle of restricting non-essential goods will stay until lockdown ends on 9 November.
Plaid said it showed building public trust was vital while the Conservatives called the rules "absolute madness".
The new guidance, issued after meetings with businesses and trade unions, follows a backlash after supermarkets closed off sections of their shops selling clothes and other items.
Earlier, business groups had appealed for customers to be "trusted to make their own decisions" on what was essential to them.
In a statement, the Welsh Government said it had "positive discussions" and that it had "clarified that a sensible system should be introduced whereby customers can ask to buy non-essential items by exception under the regulations".
"We are hopeful this provides a workable solution for retailers and customers," it said.
"However, we cannot move away from the central principle that retailers must restrict the sale of non-essential goods for the duration of the firebreak.
"We continue to work closely with the sector and would stress that these restrictions are in place to stop the spread of coronavirus and save lives.
"We are asking the public to continue to support the effort by restricting unnecessary journeys and shopping ."
Ministers issued a list that "we consider that the regulations allow" to be sold in supermarkets:
- Food and drink
- Products linked to the sale of food and drink - mainly disposable items used for the preparation and storage of food like kitchen foil, food bags and cling film but also basic products necessary to prepare and eat food and drink
- Products for washing clothes and for cleaning and maintaining the home, including batteries, light bulbs and fuel
- Toiletries and cosmetic products, including toilet rolls and sanitary products
- Pharmaceutical products
- Baby products including equipment, clothes and nappies
- Newspapers and magazines
- Stationery and greetings cards
Initially, the Welsh Government said supermarkets and department stores should close off sections of their stores, including clothing aisles.
Officials say there will be further discussions with supermarkets over coming days on how to implement the changes.
Earlier on Tuesday, retailers made their own proposals to "resolve confusion" over sales of non-essential items during Wales' lockdown.
Stores said such items could remain on shelves and not be cordoned off, with signs instead advising customers to put off non-essential purchases.
"The final liability ought to rest with the customer," retailers said.
Plaid Cymru's health spokesman Rhun ap Iorwerth said the fallout should remind the Welsh Government of the importance of "building public trust".
The Welsh Conservative leader Paul Davies has called for the Senedd to be recalled to discuss the rules.