Issue with rounding on percent discounts

Hi there,

I think I have found an issue with the calculation for discounts.
For example with a 5% discount on the total of 97.05 the plugin is taking off a total of 4.86. You can do this on a calculator and it shows as 4.8525. I have put the amount into 4 decimals on the website as well to check and the amount reported comes out as 4.8525 when displayed as 4 decimals. The plugin appears to be rounding it up incorrrectly though. To check if this was plugin related or woo was rounding this up I created my own 5% discount field, deactivated the plugin and it correctly reports the discount as 4.85. This is quite a big issue as it results in discrepancies when the data has to be imported into an invoice system.