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 $92.48   3.490%   $95.7076   $95.71   $95.70   $95.70  
  Purchase #2 $115.43   3.773%   $119.7852   $119.79   $119.80   $119.80  
  Purchase #3 $9.97   5.229%   $10.4913   $10.49   $10.50   $10.50  
  Purchase #4 $42.40   3.258%   $43.7814   $43.78   $43.80   $43.80  
  Purchase #5 $36.83   13.275%   $41.7192   $41.72   $41.70   $41.70  
  Purchase #6 $248.95   4.140%   $259.2565   $259.26   $259.25   $259.30  
  Purchase #7 $179.61   8.134%   $194.2195   $194.22   $194.20   $194.20  
  7 purchase totals = $725.67       $764.9607   $764.97   $764.95   $765.00