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 $207.76   8.627%   $225.6835   $225.68   $225.70   $225.70  
  Purchase #2 $90.98   3.494%   $94.1588   $94.16   $94.15   $94.20  
  Purchase #3 $207.42   8.262%   $224.557   $224.56   $224.55   $224.60  
  Purchase #4 $78.68   7.168%   $84.3198   $84.32   $84.30   $84.30  
  Purchase #5 $137.81   4.718%   $144.3119   $144.31   $144.30   $144.30  
  Purchase #6 $94.53   10.734%   $104.6769   $104.68   $104.70   $104.70  
  Purchase #7 $227.54   9.259%   $248.6079   $248.61   $248.60   $248.60  
  7 purchase totals = $1,044.72       $1,126.3158   $1,126.32   $1,126.30   $1,126.40