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 $46.25   7.653%   $49.7895   $49.79   $49.80   $49.80  
  Purchase #2 $14.85   13.820%   $16.9023   $16.90   $16.90   $16.90  
  Purchase #3 $127.27   7.692%   $137.0596   $137.06   $137.05   $137.10  
  Purchase #4 $153.70   12.719%   $173.2491   $173.25   $173.25   $173.20  
  Purchase #5 $214.87   5.857%   $227.4549   $227.45   $227.45   $227.50  
  Purchase #6 $216.31   9.681%   $237.251   $237.25   $237.25   $237.30  
  Purchase #7 $58.80   3.626%   $60.9321   $60.93   $60.95   $60.90  
  7 purchase totals = $832.05       $902.6385   $902.63   $902.65   $902.70