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 $191.34   7.665%   $206.0062   $206.01   $206.00   $206.00  
  Purchase #2 $75.67   8.867%   $82.3797   $82.38   $82.40   $82.40  
  Purchase #3 $185.93   7.285%   $199.475   $199.48   $199.50   $199.50  
  Purchase #4 $25.43   3.229%   $26.2511   $26.25   $26.25   $26.30  
  Purchase #5 $177.43   3.568%   $183.7607   $183.76   $183.75   $183.80  
  Purchase #6 $190.57   4.571%   $199.281   $199.28   $199.30   $199.30  
  Purchase #7 $83.26   6.567%   $88.7277   $88.73   $88.75   $88.70  
  7 purchase totals = $929.63       $985.8814   $985.89   $985.95   $986.00