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 $115.53   9.543%   $126.555   $126.56   $126.55   $126.60  
  Purchase #2 $217.48   5.361%   $229.1391   $229.14   $229.15   $229.10  
  Purchase #3 $214.40   7.693%   $230.8938   $230.89   $230.90   $230.90  
  Purchase #4 $69.92   8.728%   $76.0226   $76.02   $76.00   $76.00  
  Purchase #5 $165.83   9.845%   $182.156   $182.16   $182.15   $182.20  
  Purchase #6 $193.49   6.146%   $205.3819   $205.38   $205.40   $205.40  
  Purchase #7 $185.33   10.788%   $205.3234   $205.32   $205.30   $205.30  
  7 purchase totals = $1,161.98       $1,255.4718   $1,255.47   $1,255.45   $1,255.50