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 $59.64   10.567%   $65.9422   $65.94   $65.95   $65.90  
  Purchase #2 $26.64   13.267%   $30.1743   $30.17   $30.15   $30.20  
  Purchase #3 $106.78   10.503%   $117.9951   $118.00   $118.00   $118.00  
  Purchase #4 $239.84   8.873%   $261.121   $261.12   $261.10   $261.10  
  Purchase #5 $117.83   5.746%   $124.6005   $124.60   $124.60   $124.60  
  Purchase #6 $89.76   8.818%   $97.675   $97.68   $97.70   $97.70  
  Purchase #7 $86.88   8.595%   $94.3473   $94.35   $94.35   $94.30  
  7 purchase totals = $727.37       $791.8554   $791.86   $791.85   $791.80