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 $177.54   11.864%   $198.6033   $198.60   $198.60   $198.60  
  Purchase #2 $105.63   8.210%   $114.3022   $114.30   $114.30   $114.30  
  Purchase #3 $59.34   11.847%   $66.37   $66.37   $66.35   $66.40  
  Purchase #4 $103.38   13.686%   $117.5286   $117.53   $117.55   $117.50  
  Purchase #5 $239.89   13.687%   $272.7237   $272.72   $272.70   $272.70  
  Purchase #6 $224.52   4.416%   $234.4348   $234.43   $234.45   $234.40  
  Purchase #7 $249.98   9.366%   $273.3931   $273.39   $273.40   $273.40  
  7 purchase totals = $1,160.28       $1,277.3557   $1,277.34   $1,277.35   $1,277.30