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 $117.53   5.222%   $123.6674   $123.67   $123.65   $123.70  
  Purchase #2 $48.61   13.687%   $55.2633   $55.26   $55.25   $55.30  
  Purchase #3 $73.94   6.306%   $78.6027   $78.60   $78.60   $78.60  
  Purchase #4 $150.68   4.662%   $157.7047   $157.70   $157.70   $157.70  
  Purchase #5 $24.55   3.271%   $25.353   $25.35   $25.35   $25.40  
  Purchase #6 $171.61   10.763%   $190.0804   $190.08   $190.10   $190.10  
  Purchase #7 $90.53   4.662%   $94.7505   $94.75   $94.75   $94.80  
  7 purchase totals = $677.45       $725.4220   $725.41   $725.40   $725.60