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 $239.29   5.724%   $252.987   $252.99   $253.00   $253.00  
  Purchase #2 $119.71   11.598%   $133.594   $133.59   $133.60   $133.60  
  Purchase #3 $230.79   6.762%   $246.396   $246.40   $246.40   $246.40  
  Purchase #4 $140.64   11.271%   $156.4915   $156.49   $156.50   $156.50  
  Purchase #5 $68.75   8.217%   $74.3992   $74.40   $74.40   $74.40  
  Purchase #6 $65.58   7.868%   $70.7398   $70.74   $70.75   $70.70  
  Purchase #7 $160.44   6.790%   $171.3339   $171.33   $171.35   $171.30  
  7 purchase totals = $1,025.20       $1,105.9414   $1,105.94   $1,106.00   $1,105.90