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 $55.48   12.271%   $62.288   $62.29   $62.30   $62.30  
  Purchase #2 $198.35   7.214%   $212.659   $212.66   $212.65   $212.70  
  Purchase #3 $208.95   5.647%   $220.7494   $220.75   $220.75   $220.70  
  Purchase #4 $124.74   6.147%   $132.4078   $132.41   $132.40   $132.40  
  Purchase #5 $202.49   12.151%   $227.0946   $227.09   $227.10   $227.10  
  Purchase #6 $250.25   4.224%   $260.8206   $260.82   $260.80   $260.80  
  Purchase #7 $136.77   3.208%   $141.1576   $141.16   $141.15   $141.20  
  7 purchase totals = $1,177.03       $1,257.1770   $1,257.18   $1,257.15   $1,257.20