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 $111.67   12.567%   $125.7036   $125.70   $125.70   $125.70  
  Purchase #2 $53.77   8.490%   $58.3351   $58.34   $58.35   $58.30  
  Purchase #3 $244.59   7.516%   $262.9734   $262.97   $262.95   $263.00  
  Purchase #4 $79.42   12.829%   $89.6088   $89.61   $89.60   $89.60  
  Purchase #5 $186.28   11.705%   $208.0841   $208.08   $208.10   $208.10  
  Purchase #6 $82.30   4.424%   $85.941   $85.94   $85.95   $85.90  
  Purchase #7 $91.77   13.755%   $104.393   $104.39   $104.40   $104.40  
  7 purchase totals = $849.80       $935.0390   $935.03   $935.05   $935.00