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 $62.29   4.713%   $65.2257   $65.23   $65.25   $65.20  
  Purchase #2 $98.68   5.434%   $104.0423   $104.04   $104.05   $104.00  
  Purchase #3 $205.96   4.212%   $214.635   $214.64   $214.65   $214.60  
  Purchase #4 $40.36   8.312%   $43.7147   $43.71   $43.70   $43.70  
  Purchase #5 $196.55   9.209%   $214.6503   $214.65   $214.65   $214.70  
  Purchase #6 $163.38   8.554%   $177.3555   $177.36   $177.35   $177.40  
  Purchase #7 $88.96   13.468%   $100.9411   $100.94   $100.95   $100.90  
  7 purchase totals = $856.18       $920.5646   $920.57   $920.60   $920.50