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 $59.51   6.279%   $63.2466   $63.25   $63.25   $63.20  
  Purchase #2 $32.96   6.619%   $35.1416   $35.14   $35.15   $35.10  
  Purchase #3 $188.64   4.372%   $196.8873   $196.89   $196.90   $196.90  
  Purchase #4 $199.32   4.720%   $208.7279   $208.73   $208.75   $208.70  
  Purchase #5 $102.44   12.212%   $114.95   $114.95   $114.95   $115.00  
  Purchase #6 $176.96   6.788%   $188.972   $188.97   $188.95   $189.00  
  Purchase #7 $209.69   4.322%   $218.7528   $218.75   $218.75   $218.80  
  7 purchase totals = $969.52       $1,026.6782   $1,026.68   $1,026.70   $1,026.70