Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $59.49   5.614%   $62.8298   $62.83   $62.85   $62.80  
  Purchase #2 $242.86   4.629%   $254.102   $254.10   $254.10   $254.10  
  Purchase #3 $65.92   12.651%   $74.2595   $74.26   $74.25   $74.30  
  Purchase #4 $45.68   13.827%   $51.9962   $52.00   $52.00   $52.00  
  Purchase #5 $132.87   11.141%   $147.673   $147.67   $147.65   $147.70  
  Purchase #6 $153.58   7.152%   $164.564   $164.56   $164.55   $164.60  
  Purchase #7 $234.52   4.118%   $244.1775   $244.18   $244.20   $244.20  
  7 purchase totals = $934.92       $999.6020   $999.60   $999.60   $999.70