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 $85.56   8.306%   $92.6666   $92.67   $92.65   $92.70  
  Purchase #2 $121.51   10.638%   $134.4362   $134.44   $134.45   $134.40  
  Purchase #3 $133.83   8.187%   $144.7867   $144.79   $144.80   $144.80  
  Purchase #4 $208.90   4.646%   $218.6055   $218.61   $218.60   $218.60  
  Purchase #5 $156.41   5.287%   $164.6794   $164.68   $164.70   $164.70  
  Purchase #6 $188.57   13.659%   $214.3268   $214.33   $214.35   $214.30  
  Purchase #7 $206.36   13.240%   $233.6821   $233.68   $233.70   $233.70  
  7 purchase totals = $1,101.14       $1,203.1833   $1,203.20   $1,203.25   $1,203.20