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 $182.70   7.602%   $196.5889   $196.59   $196.60   $196.60  
  Purchase #2 $22.32   6.156%   $23.694   $23.69   $23.70   $23.70  
  Purchase #3 $239.51   10.643%   $265.001   $265.00   $265.00   $265.00  
  Purchase #4 $248.61   5.605%   $262.5446   $262.54   $262.55   $262.50  
  Purchase #5 $79.40   7.809%   $85.6003   $85.60   $85.60   $85.60  
  Purchase #6 $213.90   7.664%   $230.2933   $230.29   $230.30   $230.30  
  Purchase #7 $11.70   10.773%   $12.9604   $12.96   $12.95   $13.00  
  7 purchase totals = $998.14       $1,076.6825   $1,076.67   $1,076.70   $1,076.70