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 $246.90   6.104%   $261.9708   $261.97   $261.95   $262.00  
  Purchase #2 $146.73   13.441%   $166.452   $166.45   $166.45   $166.50  
  Purchase #3 $134.90   6.139%   $143.1815   $143.18   $143.20   $143.20  
  Purchase #4 $74.47   5.497%   $78.5636   $78.56   $78.55   $78.60  
  Purchase #5 $180.50   7.329%   $193.7288   $193.73   $193.75   $193.70  
  Purchase #6 $177.42   11.444%   $197.7239   $197.72   $197.70   $197.70  
  Purchase #7 $153.85   5.446%   $162.2287   $162.23   $162.25   $162.20  
  7 purchase totals = $1,114.77       $1,203.8493   $1,203.84   $1,203.85   $1,203.90