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 $85.86   11.874%   $96.055   $96.06   $96.05   $96.10  
  Purchase #2 $168.99   8.171%   $182.7982   $182.80   $182.80   $182.80  
  Purchase #3 $63.35   12.323%   $71.1566   $71.16   $71.15   $71.20  
  Purchase #4 $78.91   5.523%   $83.2682   $83.27   $83.25   $83.30  
  Purchase #5 $114.93   12.413%   $129.1963   $129.20   $129.20   $129.20  
  Purchase #6 $21.62   5.544%   $22.8186   $22.82   $22.80   $22.80  
  Purchase #7 $139.93   6.260%   $148.6896   $148.69   $148.70   $148.70  
  7 purchase totals = $673.59       $733.9825   $734.00   $733.95   $734.10