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 $121.36   3.535%   $125.6501   $125.65   $125.65   $125.70  
  Purchase #2 $215.66   5.627%   $227.7952   $227.80   $227.80   $227.80  
  Purchase #3 $28.59   5.791%   $30.2456   $30.25   $30.25   $30.20  
  Purchase #4 $109.98   11.456%   $122.5793   $122.58   $122.60   $122.60  
  Purchase #5 $208.95   13.307%   $236.755   $236.76   $236.75   $236.80  
  Purchase #6 $97.31   7.795%   $104.8953   $104.90   $104.90   $104.90  
  Purchase #7 $235.72   4.139%   $245.4765   $245.48   $245.50   $245.50  
  7 purchase totals = $1,017.57       $1,093.3970   $1,093.42   $1,093.45   $1,093.50