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 $161.63   12.759%   $182.2524   $182.25   $182.25   $182.30  
  Purchase #2 $80.69   3.682%   $83.661   $83.66   $83.65   $83.70  
  Purchase #3 $97.26   9.737%   $106.7302   $106.73   $106.75   $106.70  
  Purchase #4 $99.80   7.796%   $107.5804   $107.58   $107.60   $107.60  
  Purchase #5 $102.84   11.620%   $114.79   $114.79   $114.80   $114.80  
  Purchase #6 $221.79   6.598%   $236.4237   $236.42   $236.40   $236.40  
  Purchase #7 $185.64   7.508%   $199.5779   $199.58   $199.60   $199.60  
  7 purchase totals = $949.65       $1,031.0156   $1,031.01   $1,031.05   $1,031.10