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 $149.72   11.495%   $166.9303   $166.93   $166.95   $166.90  
  Purchase #2 $145.83   13.816%   $165.9779   $165.98   $166.00   $166.00  
  Purchase #3 $83.97   13.155%   $95.0163   $95.02   $95.00   $95.00  
  Purchase #4 $124.65   4.799%   $130.632   $130.63   $130.65   $130.60  
  Purchase #5 $192.26   11.631%   $214.6218   $214.62   $214.60   $214.60  
  Purchase #6 $163.99   5.864%   $173.6064   $173.61   $173.60   $173.60  
  Purchase #7 $208.81   13.247%   $236.4711   $236.47   $236.45   $236.50  
  7 purchase totals = $1,069.23       $1,183.2558   $1,183.26   $1,183.25   $1,183.20