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 $176.75   3.152%   $182.3212   $182.32   $182.30   $182.30  
  Purchase #2 $157.86   11.302%   $175.7013   $175.70   $175.70   $175.70  
  Purchase #3 $221.69   11.289%   $246.7166   $246.72   $246.70   $246.70  
  Purchase #4 $177.54   12.223%   $199.2407   $199.24   $199.25   $199.20  
  Purchase #5 $191.30   13.291%   $216.7257   $216.73   $216.75   $216.70  
  Purchase #6 $197.31   13.570%   $224.085   $224.09   $224.10   $224.10  
  Purchase #7 $77.90   11.777%   $87.0743   $87.07   $87.05   $87.10  
  7 purchase totals = $1,200.35       $1,331.8648   $1,331.87   $1,331.85   $1,331.80