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 $241.46   8.493%   $261.9672   $261.97   $261.95   $262.00  
  Purchase #2 $140.63   8.660%   $152.8086   $152.81   $152.80   $152.80  
  Purchase #3 $134.85   6.749%   $143.951   $143.95   $143.95   $144.00  
  Purchase #4 $167.31   6.424%   $178.058   $178.06   $178.05   $178.10  
  Purchase #5 $199.72   8.351%   $216.3986   $216.40   $216.40   $216.40  
  Purchase #6 $9.37   10.513%   $10.3551   $10.36   $10.35   $10.40  
  Purchase #7 $235.89   3.673%   $244.5542   $244.55   $244.55   $244.60  
  7 purchase totals = $1,129.23       $1,208.0927   $1,208.10   $1,208.05   $1,208.30