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 $196.81   5.493%   $207.6208   $207.62   $207.60   $207.60  
  Purchase #2 $111.41   9.117%   $121.5672   $121.57   $121.55   $121.60  
  Purchase #3 $197.60   4.200%   $205.8992   $205.90   $205.90   $205.90  
  Purchase #4 $26.88   12.734%   $30.3029   $30.30   $30.30   $30.30  
  Purchase #5 $191.61   9.113%   $209.0714   $209.07   $209.05   $209.10  
  Purchase #6 $219.38   13.112%   $248.1451   $248.15   $248.15   $248.10  
  Purchase #7 $219.48   8.284%   $237.6617   $237.66   $237.65   $237.70  
  7 purchase totals = $1,163.17       $1,260.2683   $1,260.27   $1,260.20   $1,260.30