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 $72.28   5.784%   $76.4607   $76.46   $76.45   $76.50  
  Purchase #2 $119.97   4.478%   $125.3423   $125.34   $125.35   $125.30  
  Purchase #3 $26.70   13.347%   $30.2636   $30.26   $30.25   $30.30  
  Purchase #4 $30.94   10.874%   $34.3044   $34.30   $34.30   $34.30  
  Purchase #5 $71.58   3.839%   $74.328   $74.33   $74.35   $74.30  
  Purchase #6 $193.73   11.372%   $215.761   $215.76   $215.75   $215.80  
  Purchase #7 $58.96   11.445%   $65.708   $65.71   $65.70   $65.70  
  7 purchase totals = $574.16       $622.1680   $622.16   $622.15   $622.20