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 $219.86   11.222%   $244.5327   $244.53   $244.55   $244.50  
  Purchase #2 $60.27   12.308%   $67.688   $67.69   $67.70   $67.70  
  Purchase #3 $113.68   5.383%   $119.7994   $119.80   $119.80   $119.80  
  Purchase #4 $57.33   10.448%   $63.3198   $63.32   $63.30   $63.30  
  Purchase #5 $131.62   4.720%   $137.8325   $137.83   $137.85   $137.80  
  Purchase #6 $125.42   6.194%   $133.1885   $133.19   $133.20   $133.20  
  Purchase #7 $96.25   3.234%   $99.3627   $99.36   $99.35   $99.40  
  7 purchase totals = $804.43       $865.7236   $865.72   $865.75   $865.70