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 $241.79   8.368%   $262.023   $262.02   $262.00   $262.00  
  Purchase #2 $233.25   10.492%   $257.7226   $257.72   $257.70   $257.70  
  Purchase #3 $162.32   5.492%   $171.2346   $171.23   $171.25   $171.20  
  Purchase #4 $163.62   11.845%   $183.0008   $183.00   $183.00   $183.00  
  Purchase #5 $50.98   8.346%   $55.2348   $55.23   $55.25   $55.20  
  Purchase #6 $60.68   12.500%   $68.265   $68.27   $68.25   $68.30  
  Purchase #7 $216.50   3.714%   $224.5408   $224.54   $224.55   $224.50  
  7 purchase totals = $1,129.14       $1,222.0216   $1,222.01   $1,222.00   $1,221.90