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 $185.32   5.747%   $195.9703   $195.97   $195.95   $196.00  
  Purchase #2 $36.54   8.775%   $39.7464   $39.75   $39.75   $39.70  
  Purchase #3 $166.62   3.704%   $172.7916   $172.79   $172.80   $172.80  
  Purchase #4 $242.80   7.665%   $261.4106   $261.41   $261.40   $261.40  
  Purchase #5 $53.42   12.804%   $60.2599   $60.26   $60.25   $60.30  
  Purchase #6 $113.83   11.577%   $127.0081   $127.01   $127.00   $127.00  
  Purchase #7 $62.64   4.583%   $65.5108   $65.51   $65.50   $65.50  
  7 purchase totals = $861.17       $922.6977   $922.70   $922.65   $922.70