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 $114.39   4.724%   $119.7938   $119.79   $119.80   $119.80  
  Purchase #2 $218.81   10.322%   $241.3956   $241.40   $241.40   $241.40  
  Purchase #3 $6.87   12.134%   $7.7036   $7.70   $7.70   $7.70  
  Purchase #4 $181.93   7.301%   $195.2127   $195.21   $195.20   $195.20  
  Purchase #5 $154.73   11.873%   $173.1011   $173.10   $173.10   $173.10  
  Purchase #6 $176.47   10.149%   $194.3799   $194.38   $194.40   $194.40  
  Purchase #7 $102.57   12.524%   $115.4159   $115.42   $115.40   $115.40  
  7 purchase totals = $955.77       $1,047.0026   $1,047.00   $1,047.00   $1,047.00