Need help with XSLT Transformation

Here's my dilema. I have a Transactions Node with an unknown amount of transaction child nodes. I need to transform this into a node called 'Buckets', who has 'Bucket' children. Each bucket can hold at the most 4 transactions. I can't seem to figure out how to do this. Anyone have any ideas?

Before:

Code:

---

<Transactions>
    <Transaction>1</Transaction>
    <Transaction>2</Transaction>
    <Transaction>3</Transaction>
    <Transaction>4</Transaction>
    <Transaction>5</Transaction>
</Transactions>

---

After:

Code:

---

<Buckets>
    <Bucket>
        <Transaction>1</Transaction>
        <Transaction>2</Transaction>
        <Transaction>3</Transaction>
        <Transaction>4</Transaction>
    </Bucket>
    <Bucket>
        <Transaction>5</Transaction>
    </Bucket>
</Buckets>

---