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 $228.66   5.622%   $241.5153   $241.52   $241.50   $241.50  
  Purchase #2 $142.38   7.246%   $152.6969   $152.70   $152.70   $152.70  
  Purchase #3 $182.40   9.322%   $199.4033   $199.40   $199.40   $199.40  
  Purchase #4 $82.54   3.168%   $85.1549   $85.15   $85.15   $85.20  
  Purchase #5 $122.97   8.647%   $133.6032   $133.60   $133.60   $133.60  
  Purchase #6 $235.99   6.742%   $251.9004   $251.90   $251.90   $251.90  
  Purchase #7 $108.38   5.462%   $114.2997   $114.30   $114.30   $114.30  
  7 purchase totals = $1,103.32       $1,178.5737   $1,178.57   $1,178.55   $1,178.60