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 $229.97   6.413%   $244.718   $244.72   $244.70   $244.70  
  Purchase #2 $47.27   8.242%   $51.166   $51.17   $51.15   $51.20  
  Purchase #3 $225.61   11.175%   $250.8219   $250.82   $250.80   $250.80  
  Purchase #4 $208.66   7.473%   $224.2532   $224.25   $224.25   $224.30  
  Purchase #5 $200.54   6.843%   $214.263   $214.26   $214.25   $214.30  
  Purchase #6 $54.41   4.231%   $56.7121   $56.71   $56.70   $56.70  
  Purchase #7 $211.65   10.384%   $233.6277   $233.63   $233.65   $233.60  
  7 purchase totals = $1,178.11       $1,275.5619   $1,275.56   $1,275.50   $1,275.60