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 $205.66   3.252%   $212.3481   $212.35   $212.35   $212.30  
  Purchase #2 $10.42   6.104%   $11.056   $11.06   $11.05   $11.10  
  Purchase #3 $42.38   3.593%   $43.9027   $43.90   $43.90   $43.90  
  Purchase #4 $6.99   3.560%   $7.2388   $7.24   $7.25   $7.20  
  Purchase #5 $139.68   8.237%   $151.1854   $151.19   $151.20   $151.20  
  Purchase #6 $111.32   13.817%   $126.7011   $126.70   $126.70   $126.70  
  Purchase #7 $157.53   10.622%   $174.2628   $174.26   $174.25   $174.30  
  7 purchase totals = $673.98       $726.6949   $726.70   $726.70   $726.70