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 $85.63   11.648%   $95.6042   $95.60   $95.60   $95.60  
  Purchase #2 $130.61   3.405%   $135.0573   $135.06   $135.05   $135.10  
  Purchase #3 $136.71   13.277%   $154.861   $154.86   $154.85   $154.90  
  Purchase #4 $167.84   9.593%   $183.9409   $183.94   $183.95   $183.90  
  Purchase #5 $96.71   13.571%   $109.8345   $109.83   $109.85   $109.80  
  Purchase #6 $53.88   13.310%   $61.0514   $61.05   $61.05   $61.10  
  Purchase #7 $30.36   12.444%   $34.138   $34.14   $34.15   $34.10  
  7 purchase totals = $701.74       $774.4873   $774.48   $774.50   $774.50