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 $55.93   6.330%   $59.4704   $59.47   $59.45   $59.50  
  Purchase #2 $87.63   6.751%   $93.5459   $93.55   $93.55   $93.50  
  Purchase #3 $90.58   3.866%   $94.0818   $94.08   $94.10   $94.10  
  Purchase #4 $172.31   8.441%   $186.8547   $186.85   $186.85   $186.90  
  Purchase #5 $202.75   5.115%   $213.1207   $213.12   $213.10   $213.10  
  Purchase #6 $190.26   6.455%   $202.5413   $202.54   $202.55   $202.50  
  Purchase #7 $96.56   8.141%   $104.4209   $104.42   $104.40   $104.40  
  7 purchase totals = $896.02       $954.0357   $954.03   $954.00   $954.00