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 $246.52   6.441%   $262.3984   $262.40   $262.40   $262.40  
  Purchase #2 $91.99   13.589%   $104.4905   $104.49   $104.50   $104.50  
  Purchase #3 $121.87   11.850%   $136.3116   $136.31   $136.30   $136.30  
  Purchase #4 $169.76   3.110%   $175.0395   $175.04   $175.05   $175.00  
  Purchase #5 $246.81   13.595%   $280.3638   $280.36   $280.35   $280.40  
  Purchase #6 $250.88   11.650%   $280.1075   $280.11   $280.10   $280.10  
  Purchase #7 $214.64   4.726%   $224.7839   $224.78   $224.80   $224.80  
  7 purchase totals = $1,342.47       $1,463.4952   $1,463.49   $1,463.50   $1,463.50