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 $102.97   10.684%   $113.9713   $113.97   $113.95   $114.00  
  Purchase #2 $217.87   7.324%   $233.8268   $233.83   $233.85   $233.80  
  Purchase #3 $249.63   3.529%   $258.4394   $258.44   $258.45   $258.40  
  Purchase #4 $155.68   8.861%   $169.4748   $169.47   $169.45   $169.50  
  Purchase #5 $175.70   6.814%   $187.6722   $187.67   $187.65   $187.70  
  Purchase #6 $45.60   5.306%   $48.0195   $48.02   $48.00   $48.00  
  Purchase #7 $199.60   4.231%   $208.0451   $208.05   $208.05   $208.00  
  7 purchase totals = $1,147.05       $1,219.4491   $1,219.45   $1,219.40   $1,219.40