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 $69.80   5.458%   $73.6097   $73.61   $73.60   $73.60  
  Purchase #2 $236.76   12.630%   $266.6628   $266.66   $266.65   $266.70  
  Purchase #3 $209.65   7.539%   $225.4555   $225.46   $225.45   $225.50  
  Purchase #4 $17.38   7.633%   $18.7066   $18.71   $18.70   $18.70  
  Purchase #5 $86.60   10.422%   $95.6255   $95.63   $95.65   $95.60  
  Purchase #6 $238.83   5.542%   $252.066   $252.07   $252.05   $252.10  
  Purchase #7 $22.52   6.542%   $23.9933   $23.99   $24.00   $24.00  
  7 purchase totals = $881.54       $956.1194   $956.13   $956.10   $956.20