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 $193.28   3.347%   $199.7491   $199.75   $199.75   $199.70  
  Purchase #2 $242.82   4.334%   $253.3438   $253.34   $253.35   $253.30  
  Purchase #3 $76.81   10.571%   $84.9296   $84.93   $84.95   $84.90  
  Purchase #4 $160.55   8.102%   $173.5578   $173.56   $173.55   $173.60  
  Purchase #5 $107.26   6.518%   $114.2512   $114.25   $114.25   $114.30  
  Purchase #6 $130.36   9.195%   $142.3466   $142.35   $142.35   $142.30  
  Purchase #7 $54.67   7.410%   $58.721   $58.72   $58.70   $58.70  
  7 purchase totals = $965.75       $1,026.8991   $1,026.90   $1,026.90   $1,026.80