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 $61.95   12.702%   $69.8189   $69.82   $69.80   $69.80  
  Purchase #2 $42.45   10.381%   $46.8567   $46.86   $46.85   $46.90  
  Purchase #3 $16.26   8.820%   $17.6941   $17.69   $17.70   $17.70  
  Purchase #4 $222.96   5.705%   $235.6799   $235.68   $235.70   $235.70  
  Purchase #5 $75.44   3.245%   $77.888   $77.89   $77.90   $77.90  
  Purchase #6 $167.40   5.306%   $176.2822   $176.28   $176.30   $176.30  
  Purchase #7 $109.49   4.785%   $114.7291   $114.73   $114.75   $114.70  
  7 purchase totals = $695.95       $738.9489   $738.95   $739.00   $739.00