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 $201.76   11.465%   $224.8918   $224.89   $224.90   $224.90  
  Purchase #2 $168.39   11.617%   $187.9519   $187.95   $187.95   $188.00  
  Purchase #3 $238.60   11.417%   $265.841   $265.84   $265.85   $265.80  
  Purchase #4 $199.93   3.244%   $206.4157   $206.42   $206.40   $206.40  
  Purchase #5 $184.65   11.161%   $205.2588   $205.26   $205.25   $205.30  
  Purchase #6 $221.76   5.240%   $233.3802   $233.38   $233.40   $233.40  
  Purchase #7 $132.76   12.131%   $148.8651   $148.87   $148.85   $148.90  
  7 purchase totals = $1,347.85       $1,472.6045   $1,472.61   $1,472.60   $1,472.70