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 $54.44   7.544%   $58.547   $58.55   $58.55   $58.50  
  Purchase #2 $66.67   4.372%   $69.5848   $69.58   $69.60   $69.60  
  Purchase #3 $9.68   11.105%   $10.755   $10.76   $10.75   $10.80  
  Purchase #4 $96.94   4.739%   $101.534   $101.53   $101.55   $101.50  
  Purchase #5 $220.46   5.103%   $231.7101   $231.71   $231.70   $231.70  
  Purchase #6 $105.96   12.213%   $118.9009   $118.90   $118.90   $118.90  
  Purchase #7 $102.53   11.643%   $114.4676   $114.47   $114.45   $114.50  
  7 purchase totals = $656.68       $705.4994   $705.50   $705.50   $705.50