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 $119.48   5.164%   $125.6499   $125.65   $125.65   $125.60  
  Purchase #2 $48.69   10.247%   $53.6793   $53.68   $53.70   $53.70  
  Purchase #3 $181.63   7.108%   $194.5403   $194.54   $194.55   $194.50  
  Purchase #4 $212.56   3.433%   $219.8572   $219.86   $219.85   $219.90  
  Purchase #5 $81.35   3.466%   $84.1696   $84.17   $84.15   $84.20  
  Purchase #6 $56.76   3.156%   $58.5513   $58.55   $58.55   $58.60  
  Purchase #7 $67.85   7.417%   $72.8824   $72.88   $72.90   $72.90  
  7 purchase totals = $768.32       $809.3300   $809.33   $809.35   $809.40