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 $214.27   5.694%   $226.4705   $226.47   $226.45   $226.50  
  Purchase #2 $161.93   4.779%   $169.6686   $169.67   $169.65   $169.70  
  Purchase #3 $176.82   9.669%   $193.9167   $193.92   $193.90   $193.90  
  Purchase #4 $136.73   11.513%   $152.4717   $152.47   $152.45   $152.50  
  Purchase #5 $224.25   4.730%   $234.857   $234.86   $234.85   $234.90  
  Purchase #6 $241.41   8.537%   $262.0192   $262.02   $262.00   $262.00  
  Purchase #7 $169.63   12.796%   $191.3359   $191.34   $191.35   $191.30  
  7 purchase totals = $1,325.04       $1,430.7396   $1,430.75   $1,430.65   $1,430.80