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 $182.36   8.399%   $197.6764   $197.68   $197.70   $197.70  
  Purchase #2 $57.61   10.172%   $63.4701   $63.47   $63.45   $63.50  
  Purchase #3 $103.61   9.843%   $113.8083   $113.81   $113.80   $113.80  
  Purchase #4 $234.87   11.548%   $261.9928   $261.99   $262.00   $262.00  
  Purchase #5 $221.47   12.432%   $249.0032   $249.00   $249.00   $249.00  
  Purchase #6 $215.59   11.681%   $240.7731   $240.77   $240.75   $240.80  
  Purchase #7 $60.67   7.169%   $65.0194   $65.02   $65.00   $65.00  
  7 purchase totals = $1,076.18       $1,191.7433   $1,191.74   $1,191.70   $1,191.80