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 $88.69   11.565%   $98.947   $98.95   $98.95   $98.90  
  Purchase #2 $32.44   13.129%   $36.699   $36.70   $36.70   $36.70  
  Purchase #3 $120.26   7.630%   $129.4358   $129.44   $129.45   $129.40  
  Purchase #4 $165.90   3.257%   $171.3034   $171.30   $171.30   $171.30  
  Purchase #5 $104.98   13.602%   $119.2594   $119.26   $119.25   $119.30  
  Purchase #6 $100.68   3.239%   $103.941   $103.94   $103.95   $103.90  
  Purchase #7 $248.61   4.812%   $260.5731   $260.57   $260.55   $260.60  
  7 purchase totals = $861.56       $920.1587   $920.16   $920.15   $920.10