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 $202.28   5.599%   $213.6057   $213.61   $213.60   $213.60  
  Purchase #2 $200.55   3.481%   $207.5311   $207.53   $207.55   $207.50  
  Purchase #3 $156.35   12.481%   $175.864   $175.86   $175.85   $175.90  
  Purchase #4 $177.85   4.486%   $185.8284   $185.83   $185.85   $185.80  
  Purchase #5 $229.74   13.694%   $261.2006   $261.20   $261.20   $261.20  
  Purchase #6 $194.61   9.498%   $213.0941   $213.09   $213.10   $213.10  
  Purchase #7 $204.84   4.823%   $214.7194   $214.72   $214.70   $214.70  
  7 purchase totals = $1,366.22       $1,471.8433   $1,471.84   $1,471.85   $1,471.80