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 $184.49   9.440%   $201.9059   $201.91   $201.90   $201.90  
  Purchase #2 $249.56   6.531%   $265.8588   $265.86   $265.85   $265.90  
  Purchase #3 $82.26   5.511%   $86.7933   $86.79   $86.80   $86.80  
  Purchase #4 $201.72   6.488%   $214.8076   $214.81   $214.80   $214.80  
  Purchase #5 $149.32   8.750%   $162.3855   $162.39   $162.40   $162.40  
  Purchase #6 $35.47   9.544%   $38.8553   $38.86   $38.85   $38.90  
  Purchase #7 $236.63   10.554%   $261.6039   $261.60   $261.60   $261.60  
  7 purchase totals = $1,139.45       $1,232.2103   $1,232.22   $1,232.20   $1,232.30