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 $61.90   11.276%   $68.8798   $68.88   $68.90   $68.90  
  Purchase #2 $191.67   8.867%   $208.6654   $208.67   $208.65   $208.70  
  Purchase #3 $50.37   12.870%   $56.8526   $56.85   $56.85   $56.90  
  Purchase #4 $248.73   5.402%   $262.1664   $262.17   $262.15   $262.20  
  Purchase #5 $130.94   4.835%   $137.2709   $137.27   $137.25   $137.30  
  Purchase #6 $112.66   4.780%   $118.0451   $118.05   $118.05   $118.00  
  Purchase #7 $228.90   13.583%   $259.9915   $259.99   $260.00   $260.00  
  7 purchase totals = $1,025.17       $1,111.8717   $1,111.88   $1,111.85   $1,112.00