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 $118.64   9.294%   $129.6664   $129.67   $129.65   $129.70  
  Purchase #2 $123.50   7.733%   $133.0503   $133.05   $133.05   $133.10  
  Purchase #3 $44.94   9.250%   $49.097   $49.10   $49.10   $49.10  
  Purchase #4 $183.64   13.674%   $208.7509   $208.75   $208.75   $208.80  
  Purchase #5 $119.27   10.448%   $131.7313   $131.73   $131.75   $131.70  
  Purchase #6 $179.41   9.273%   $196.0467   $196.05   $196.05   $196.00  
  Purchase #7 $178.63   11.724%   $199.5726   $199.57   $199.55   $199.60  
  7 purchase totals = $948.03       $1,047.9152   $1,047.92   $1,047.90   $1,048.00