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 $86.72   10.218%   $95.581   $95.58   $95.60   $95.60  
  Purchase #2 $224.63   8.495%   $243.7123   $243.71   $243.70   $243.70  
  Purchase #3 $63.95   9.831%   $70.2369   $70.24   $70.25   $70.20  
  Purchase #4 $70.39   8.484%   $76.3619   $76.36   $76.35   $76.40  
  Purchase #5 $202.62   4.407%   $211.5495   $211.55   $211.55   $211.50  
  Purchase #6 $90.97   10.432%   $100.46   $100.46   $100.45   $100.50  
  Purchase #7 $76.39   3.376%   $78.9689   $78.97   $78.95   $79.00  
  7 purchase totals = $815.67       $876.8705   $876.87   $876.85   $876.90