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 $192.75   4.602%   $201.6204   $201.62   $201.60   $201.60  
  Purchase #2 $177.93   12.223%   $199.6784   $199.68   $199.70   $199.70  
  Purchase #3 $171.71   12.686%   $193.4931   $193.49   $193.50   $193.50  
  Purchase #4 $34.26   3.533%   $35.4704   $35.47   $35.45   $35.50  
  Purchase #5 $124.25   3.432%   $128.5143   $128.51   $128.50   $128.50  
  Purchase #6 $100.33   6.745%   $107.0973   $107.10   $107.10   $107.10  
  Purchase #7 $66.72   4.609%   $69.7951   $69.80   $69.80   $69.80  
  7 purchase totals = $867.95       $935.6690   $935.67   $935.65   $935.70