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 $124.98   6.616%   $133.2487   $133.25   $133.25   $133.20  
  Purchase #2 $77.69   5.544%   $81.9971   $82.00   $82.00   $82.00  
  Purchase #3 $90.98   9.335%   $99.473   $99.47   $99.45   $99.50  
  Purchase #4 $99.83   11.154%   $110.965   $110.97   $110.95   $111.00  
  Purchase #5 $69.27   5.802%   $73.289   $73.29   $73.30   $73.30  
  Purchase #6 $200.70   11.175%   $223.1282   $223.13   $223.15   $223.10  
  Purchase #7 $10.29   6.434%   $10.9521   $10.95   $10.95   $11.00  
  7 purchase totals = $673.74       $733.0531   $733.06   $733.05   $733.10