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 $213.94   5.108%   $224.8681   $224.87   $224.85   $224.90  
  Purchase #2 $231.92   3.330%   $239.6429   $239.64   $239.65   $239.60  
  Purchase #3 $60.70   11.270%   $67.5409   $67.54   $67.55   $67.50  
  Purchase #4 $130.53   12.288%   $146.5695   $146.57   $146.55   $146.60  
  Purchase #5 $139.77   9.149%   $152.5576   $152.56   $152.55   $152.60  
  Purchase #6 $141.31   9.251%   $154.3826   $154.38   $154.40   $154.40  
  Purchase #7 $206.99   4.346%   $215.9858   $215.99   $216.00   $216.00  
  7 purchase totals = $1,125.16       $1,201.5474   $1,201.55   $1,201.55   $1,201.60