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 $59.65   13.208%   $67.5286   $67.53   $67.55   $67.50  
  Purchase #2 $200.42   7.365%   $215.1809   $215.18   $215.20   $215.20  
  Purchase #3 $154.37   11.330%   $171.8601   $171.86   $171.85   $171.90  
  Purchase #4 $46.44   5.394%   $48.945   $48.95   $48.95   $48.90  
  Purchase #5 $243.38   8.710%   $264.5784   $264.58   $264.60   $264.60  
  Purchase #6 $213.28   3.746%   $221.2695   $221.27   $221.25   $221.30  
  Purchase #7 $202.87   12.234%   $227.6891   $227.69   $227.70   $227.70  
  7 purchase totals = $1,120.41       $1,217.0516   $1,217.06   $1,217.10   $1,217.10