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 $175.60   12.172%   $196.974   $196.97   $196.95   $197.00  
  Purchase #2 $48.86   6.859%   $52.2113   $52.21   $52.20   $52.20  
  Purchase #3 $32.79   13.615%   $37.2544   $37.25   $37.25   $37.30  
  Purchase #4 $167.27   13.674%   $190.1425   $190.14   $190.15   $190.10  
  Purchase #5 $230.94   9.750%   $253.4567   $253.46   $253.45   $253.50  
  Purchase #6 $95.81   5.506%   $101.0853   $101.09   $101.10   $101.10  
  Purchase #7 $114.67   6.625%   $122.2669   $122.27   $122.25   $122.30  
  7 purchase totals = $865.94       $953.3911   $953.39   $953.35   $953.50