Truncate scaled value unit to maximum of two decimals

ie truncate 12.50001234 to 12.5

When using imperial, the scalling calculation rounding results in value unit
having extra decimal when converted back to imperial

+ related spec

app/services/variant_units/option_value_namer.rb

@@ -56,7 +56,7 @@ module VariantUnits
     def option_value_value_unit_scaled
       unit_scale, unit_name = scale_for_unit_value
 
-      value = BigDecimal(@variant.unit_value / unit_scale, 6)
+      value = BigDecimal(@variant.unit_value / unit_scale, 6).truncate(2)
 
       [value, unit_name]
     end

spec/services/variant_units/option_value_namer_spec.rb

@@ -145,6 +145,15 @@ module VariantUnits
         allow(v).to receive(:unit_value) { nil }
         expect(subject.send(:option_value_value_unit)).to eq [nil, nil]
       end
+
+      it "truncates value to 2 decimals maximum" do
+        oz_scale = 28.35
+        p = double(:product, variant_unit: 'weight', variant_unit_scale: oz_scale)
+        allow(v).to receive(:product) { p }
+        # The unit_value is stored rounded to 2 decimals
+        allow(v).to receive(:unit_value) { (12.5 * oz_scale).round(2) }
+        expect(subject.send(:option_value_value_unit)).to eq [BigDecimal(12.5, 6), 'oz']
+      end
     end
   end
 end