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 $60.46   4.119%   $62.9503   $62.95   $62.95   $63.00  
  Purchase #2 $62.49   7.626%   $67.2555   $67.26   $67.25   $67.30  
  Purchase #3 $106.76   5.874%   $113.0311   $113.03   $113.05   $113.00  
  Purchase #4 $222.87   8.561%   $241.9499   $241.95   $241.95   $241.90  
  Purchase #5 $85.41   3.833%   $88.6838   $88.68   $88.70   $88.70  
  Purchase #6 $76.45   6.539%   $81.4491   $81.45   $81.45   $81.40  
  Purchase #7 $95.48   5.518%   $100.7486   $100.75   $100.75   $100.70  
  7 purchase totals = $709.92       $756.0683   $756.07   $756.10   $756.00