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 $119.80   4.346%   $125.0065   $125.01   $125.00   $125.00  
  Purchase #2 $123.54   10.711%   $136.7724   $136.77   $136.75   $136.80  
  Purchase #3 $58.85   5.814%   $62.2715   $62.27   $62.25   $62.30  
  Purchase #4 $76.58   6.177%   $81.3103   $81.31   $81.30   $81.30  
  Purchase #5 $32.60   9.716%   $35.7674   $35.77   $35.75   $35.80  
  Purchase #6 $62.38   10.770%   $69.0983   $69.10   $69.10   $69.10  
  Purchase #7 $87.59   7.764%   $94.3905   $94.39   $94.40   $94.40  
  7 purchase totals = $561.34       $604.6169   $604.62   $604.55   $604.70