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 $23.97   8.603%   $26.0321   $26.03   $26.05   $26.00  
  Purchase #2 $119.76   6.243%   $127.2366   $127.24   $127.25   $127.20  
  Purchase #3 $239.63   5.671%   $253.2194   $253.22   $253.20   $253.20  
  Purchase #4 $73.25   10.772%   $81.1405   $81.14   $81.15   $81.10  
  Purchase #5 $199.31   10.274%   $219.7871   $219.79   $219.80   $219.80  
  Purchase #6 $119.36   10.610%   $132.0241   $132.02   $132.00   $132.00  
  Purchase #7 $24.86   8.705%   $27.0241   $27.02   $27.00   $27.00  
  7 purchase totals = $800.14       $866.4639   $866.46   $866.45   $866.30