The rounding variance is the difference in reported tax on the Sales Summary and Tax reports. These reports calculate tax differently, so there may be very small variations in the total due to how the total is rounded off.
Tax Total on the Sales Summary Report
The Sales Summary reports on actual tax collected from customers on each order. The tax collected from a customer is the tax on sum total of sales calculated to the fourth digit and then rounded to the second digit.
Tax Total on the Tax Report
The Tax Report calculates taxes on individual items to the fourth digit, sums them up, and rounds them to the second digit.