You need to raise this with the teacher. Please don't be afraid to do so as it's not a complaint, just something you wish to make them aware of. If it's affecting your child and they haven't yet developed the confidence to tell their teacher, you need to advocate for them. Simply outline it how you have to us, that the children on their table keep asking them to share their answers. It use to just be one child, but now it's everyone on their table all the time and it's starting to distress your child.
It would be useful to ask your child exactly what it is that they don't like about the situation, as this will help the teacher understand how they feel and how best to go about resolving the problem. Are they afraid of getting into trouble for sharing their answers? Is the constant pestering affecting their ability to concentrate? Do they simply feel an injustice that they are working hard to solve the answers, while their peers aren't bothering as they think they can just copy? Are they afraid to say no? All are valid feelings in these circumstances, but might change how the teacher handles the situation.
The teacher will hopefully, at the very least, keep a close eye on that table and speak firmly to the whole class about how they need to try and work out the answer for themselves, to help them with their learning. If they're stuck, that's ok but they need to ask an adult for some help. All of the children need to know it's ok to ask the adults for help and it's important to do so. The teachers need to know who needs further support grasping certain concepts. If they're just copying, they are only cheating themselves as they will continue to struggle. They're only 5/6, so they need this explicitly explaining to them.
Your child also needs to know that it's ok to say no. Maybe you could train them to put their hand up themselves if it keeps happening and, rather than "tell tales" of copying (if that's what they're afraid of) they could say "Miss Smith, Jack needs some help". That way they don't have to give their own answer up, and they're helping their peers by getting them the support they need (if they do indeed need support that is). If they don't, and they're simply being lazy, they'll soon get bored of asking once your child has repeated this process a few times and they realise they're not going to get away with copying them any more.
The teacher might even make some seating plan adjustments if they learn how uncomfortable this situation is making your child feel. It's always worth bringing such issues to their attention.