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 $214.47   5.630%   $226.5447   $226.54   $226.55   $226.50  
  Purchase #2 $51.69   9.626%   $56.6657   $56.67   $56.65   $56.70  
  Purchase #3 $37.91   5.381%   $39.9499   $39.95   $39.95   $39.90  
  Purchase #4 $152.85   4.163%   $159.2131   $159.21   $159.20   $159.20  
  Purchase #5 $174.34   4.652%   $182.4503   $182.45   $182.45   $182.50  
  Purchase #6 $81.56   8.852%   $88.7797   $88.78   $88.80   $88.80  
  Purchase #7 $250.79   4.228%   $261.3934   $261.39   $261.40   $261.40  
  7 purchase totals = $963.61       $1,014.9968   $1,014.99   $1,015.00   $1,015.00