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 $108.50   8.838%   $118.0892   $118.09   $118.10   $118.10  
  Purchase #2 $239.61   9.676%   $262.7947   $262.79   $262.80   $262.80  
  Purchase #3 $226.87   6.665%   $241.9909   $241.99   $242.00   $242.00  
  Purchase #4 $177.48   13.659%   $201.722   $201.72   $201.70   $201.70  
  Purchase #5 $72.90   9.832%   $80.0675   $80.07   $80.05   $80.10  
  Purchase #6 $105.47   8.484%   $114.4181   $114.42   $114.40   $114.40  
  Purchase #7 $122.82   10.787%   $136.0686   $136.07   $136.05   $136.10  
  7 purchase totals = $1,053.65       $1,155.1510   $1,155.15   $1,155.10   $1,155.20