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 $229.76   9.536%   $251.6699   $251.67   $251.65   $251.70  
  Purchase #2 $127.38   3.493%   $131.8294   $131.83   $131.85   $131.80  
  Purchase #3 $43.87   8.866%   $47.7595   $47.76   $47.75   $47.80  
  Purchase #4 $33.33   11.481%   $37.1566   $37.16   $37.15   $37.20  
  Purchase #5 $192.42   5.313%   $202.6433   $202.64   $202.65   $202.60  
  Purchase #6 $242.70   11.376%   $270.3096   $270.31   $270.30   $270.30  
  Purchase #7 $247.32   5.596%   $261.16   $261.16   $261.15   $261.20  
  7 purchase totals = $1,116.78       $1,202.5283   $1,202.53   $1,202.50   $1,202.60