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 $124.84   13.189%   $141.3051   $141.31   $141.30   $141.30  
  Purchase #2 $126.87   8.590%   $137.7681   $137.77   $137.75   $137.80  
  Purchase #3 $59.40   11.345%   $66.1389   $66.14   $66.15   $66.10  
  Purchase #4 $25.84   6.860%   $27.6126   $27.61   $27.60   $27.60  
  Purchase #5 $210.69   3.455%   $217.9693   $217.97   $217.95   $218.00  
  Purchase #6 $250.37   4.599%   $261.8845   $261.88   $261.90   $261.90  
  Purchase #7 $144.35   12.315%   $162.1267   $162.13   $162.15   $162.10  
  7 purchase totals = $942.36       $1,014.8052   $1,014.81   $1,014.80   $1,014.80