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 $59.75   5.214%   $62.8654   $62.87   $62.85   $62.90  
  Purchase #2 $204.53   7.614%   $220.1029   $220.10   $220.10   $220.10  
  Purchase #3 $227.36   4.433%   $237.4389   $237.44   $237.45   $237.40  
  Purchase #4 $83.67   11.808%   $93.5498   $93.55   $93.55   $93.50  
  Purchase #5 $207.85   12.834%   $234.5255   $234.53   $234.55   $234.50  
  Purchase #6 $30.68   13.450%   $34.8065   $34.81   $34.80   $34.80  
  Purchase #7 $130.29   4.491%   $136.1413   $136.14   $136.15   $136.10  
  7 purchase totals = $944.13       $1,019.4303   $1,019.44   $1,019.45   $1,019.30