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 $69.25   13.529%   $78.6188   $78.62   $78.60   $78.60  
  Purchase #2 $249.90   4.462%   $261.0505   $261.05   $261.05   $261.10  
  Purchase #3 $35.64   11.667%   $39.7981   $39.80   $39.80   $39.80  
  Purchase #4 $146.56   13.460%   $166.287   $166.29   $166.30   $166.30  
  Purchase #5 $177.85   4.819%   $186.4206   $186.42   $186.40   $186.40  
  Purchase #6 $81.47   6.421%   $86.7012   $86.70   $86.70   $86.70  
  Purchase #7 $191.39   7.716%   $206.1577   $206.16   $206.15   $206.20  
  7 purchase totals = $952.06       $1,025.0339   $1,025.04   $1,025.00   $1,025.10