Allow for additional decimal points for item prices

[JoshMcCarthy]

For my industry, and some related industries, we sell items at prices to the 4th decimal point. So USD$0.0625 per unit. Shipstation does not have the ability to account for this, and it rounds up the price on orders it imports from our SAP integration. This causes the prices to round up or down overall and makes the packing and customs lists inaccurate. If there was a way to give users the option to set decimal points to the 4th decimal, you would be able to expand your customer base to additional industries. We are currently using a workaround internally to account for the discrepancy, but this workaround limits us to only working with our local office. If it were to be fixed, we could expand our use of shipstation to other locations globally.