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 $119.47   5.266%   $125.7613   $125.76   $125.75   $125.80  
  Purchase #2 $215.45   13.540%   $244.6219   $244.62   $244.60   $244.60  
  Purchase #3 $38.97   11.460%   $43.436   $43.44   $43.45   $43.40  
  Purchase #4 $14.73   8.520%   $15.985   $15.99   $16.00   $16.00  
  Purchase #5 $27.99   6.300%   $29.7534   $29.75   $29.75   $29.80  
  Purchase #6 $205.76   8.774%   $223.8134   $223.81   $223.80   $223.80  
  Purchase #7 $44.94   11.419%   $50.0717   $50.07   $50.05   $50.10  
  7 purchase totals = $667.31       $733.4427   $733.44   $733.40   $733.50