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 $213.90   4.838%   $224.2485   $224.25   $224.25   $224.20  
  Purchase #2 $172.56   10.696%   $191.017   $191.02   $191.00   $191.00  
  Purchase #3 $76.73   10.253%   $84.5971   $84.60   $84.60   $84.60  
  Purchase #4 $119.97   5.631%   $126.7255   $126.73   $126.75   $126.70  
  Purchase #5 $49.86   5.349%   $52.527   $52.53   $52.55   $52.50  
  Purchase #6 $186.95   10.396%   $206.3853   $206.39   $206.40   $206.40  
  Purchase #7 $176.93   3.568%   $183.2429   $183.24   $183.25   $183.20  
  7 purchase totals = $996.90       $1,068.7433   $1,068.76   $1,068.80   $1,068.60