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 $97.27   8.267%   $105.3113   $105.31   $105.30   $105.30  
  Purchase #2 $186.68   9.792%   $204.9597   $204.96   $204.95   $205.00  
  Purchase #3 $107.32   7.800%   $115.691   $115.69   $115.70   $115.70  
  Purchase #4 $38.47   9.540%   $42.14   $42.14   $42.15   $42.10  
  Purchase #5 $140.28   8.633%   $152.3904   $152.39   $152.40   $152.40  
  Purchase #6 $93.76   8.217%   $101.4643   $101.46   $101.45   $101.50  
  Purchase #7 $191.78   5.848%   $202.9953   $203.00   $203.00   $203.00  
  7 purchase totals = $855.56       $924.9520   $924.95   $924.95   $925.00