XSLT 2.0 performance of convert flat XML data to heirarchical? - xslt-2.0

Question

I have data as follows:
<Root>
<Node>
<Region>Central</Region>
<Provider>A</Provider>
<Value>100</Value>
</Node>
<Node>
<Region>Central</Region>
<Provider>B</Provider>
<Value>200</Value>
</Node
<Node>
<Region>Central</Region>
<Provider>B</Provider>
<Value>250</Value>
</Node>
<Node>
<Region>Eastern</Region>
<Provider>C</Provider>
<Value>50</Value>
</Node>
</Root>
And trying to transform as:
<Root>
<Region>
<Name>Central</Name>
<Provider>
<Name>A</Name>
<Item>
<Value>100</Value>
</Item>
</Provider>
<Provider>
<Name>B</Name>
<Item>
<Value>200</Value>
</Item>
<Item>
<Value>250</Value>
</Item>
</Provider>
</Region>
<Region>
<Name>Eastern</Name>
<Provider>
<Name>C</Name>
<Item>
<Value>50</Value>
</Item>
</Provider>
</Region>
</Root>
In the past I have used Muenchian Method, but I am trying to use XSLT 2.0 construct xsl:for-each-group to accomplish the same thing without success so far.
Is it possible to use xsl:for-each-group to accomplish the above? How?
Edit
This is what I have so far, which appears to work. But, I am not sure about efficiency - specifically does using such constructs force the parser to read the entire document and sort it? The data coming in is already sorted the way I want.
<xsl:template match="Root">
<xsl:element name="Root">
<xsl:for-each-group select="Node" group-by="Region">
<xsl:element name="Region">
<xsl:element name="Name">
<xsl:value-of select="Region" />
</xsl:element>
<xsl:for-each-group select="current-group()" group-by="Provider">
<xsl:element name="Provider">
<xsl:for-each select="current-group()">
<xsl:element name="Item">
<xsl:value-of select="Value" />
</xsl:element>
</xsl:for-each>
</xsl:element>
</xsl:for-each-group>
</xsl:element>
</xsl:for-each-group>
</xsl:element>
</xsl:template>