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 $116.36   8.221%   $125.926   $125.93   $125.95   $125.90  
  Purchase #2 $66.73   10.126%   $73.4871   $73.49   $73.50   $73.50  
  Purchase #3 $17.71   8.166%   $19.1562   $19.16   $19.15   $19.20  
  Purchase #4 $74.85   6.348%   $79.6015   $79.60   $79.60   $79.60  
  Purchase #5 $85.92   4.105%   $89.447   $89.45   $89.45   $89.40  
  Purchase #6 $76.99   9.754%   $84.4996   $84.50   $84.50   $84.50  
  Purchase #7 $165.46   11.126%   $183.8691   $183.87   $183.85   $183.90  
  7 purchase totals = $604.02       $655.9865   $656.00   $656.00   $656.00