For the time being the property can be set through the underlying Kendo Chart widget. For example:

		<script>
			function OnLoad(chart) {
				var widget = chart.get_kendoWidget();
				//also applies for the minor grid lines - replace majorGridLines with minorGridLines
				//Numeric series
				widget.options.xAxis.majorGridLines.step = 5;
				widget.options.yAxis.majorGridLines.step = 5;
				//Category series
				//widget.options.categoryAxis.majorGridLines.step = 5;
				//widget.options.valueAxis.majorGridLines.step = 5;
				widget.redraw();
			}
		</script>
		<telerik:RadHtmlChart runat="server" ID="BubbleChart" Width="500" Height="400">
			<ClientEvents OnLoad="OnLoad" />
			<ChartTitle Text="Market Share Study">
			</ChartTitle>
			<PlotArea>
				<Appearance>
					<FillStyle BackgroundColor="White"></FillStyle>
				</Appearance>
				<XAxis MinValue="0" MaxValue="100" Step="10">
					<MinorGridLines Visible="false" />
				</XAxis>
				<YAxis MinValue="0" MaxValue="100" Step="10">
					<MinorGridLines Visible="false" />
				</YAxis>
				<Series>
					<telerik:BubbleSeries>
						<Appearance FillStyle-BackgroundColor="#6ab2c9">
						</Appearance>
						<TooltipsAppearance DataFormatString="Percentage of Market Share: {2}%<br /> Number of products: {0}<br /> Sales: ${1}" />
						<SeriesItems>
							<telerik:BubbleSeriesItem Size="3" X="5" Y="55" />
							<telerik:BubbleSeriesItem Size="12" X="14" Y="80" />
							<telerik:BubbleSeriesItem Size="33" X="20" Y="60" />
							<telerik:BubbleSeriesItem Size="10" X="18" Y="24" />
							<telerik:BubbleSeriesItem Size="42" X="22" Y="32" />
						</SeriesItems>
					</telerik:BubbleSeries>
				</Series>
			</PlotArea>
			<Legend>
				<Appearance Position="Right"></Appearance>
			</Legend>
		</telerik:RadHtmlChart>