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 $207.74   4.752%   $217.6118   $217.61   $217.60   $217.60  
  Purchase #2 $195.96   4.337%   $204.4588   $204.46   $204.45   $204.50  
  Purchase #3 $115.80   13.328%   $131.2338   $131.23   $131.25   $131.20  
  Purchase #4 $21.91   11.598%   $24.4511   $24.45   $24.45   $24.50  
  Purchase #5 $248.52   11.311%   $276.6301   $276.63   $276.65   $276.60  
  Purchase #6 $184.44   5.151%   $193.9405   $193.94   $193.95   $193.90  
  Purchase #7 $49.58   8.298%   $53.6941   $53.69   $53.70   $53.70  
  7 purchase totals = $1,023.95       $1,102.0202   $1,102.01   $1,102.05   $1,102.00