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 $168.31   10.327%   $185.6914   $185.69   $185.70   $185.70  
  Purchase #2 $163.83   8.105%   $177.1084   $177.11   $177.10   $177.10  
  Purchase #3 $88.92   4.609%   $93.0183   $93.02   $93.00   $93.00  
  Purchase #4 $65.81   5.486%   $69.4203   $69.42   $69.40   $69.40  
  Purchase #5 $207.41   4.206%   $216.1337   $216.13   $216.15   $216.10  
  Purchase #6 $131.94   12.556%   $148.5064   $148.51   $148.50   $148.50  
  Purchase #7 $123.71   7.412%   $132.8794   $132.88   $132.90   $132.90  
  7 purchase totals = $949.93       $1,022.7579   $1,022.76   $1,022.75   $1,022.70