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 $196.68   5.244%   $206.9939   $206.99   $207.00   $207.00  
  Purchase #2 $130.71   7.106%   $139.9983   $140.00   $140.00   $140.00  
  Purchase #3 $109.54   3.679%   $113.57   $113.57   $113.55   $113.60  
  Purchase #4 $193.27   13.508%   $219.3769   $219.38   $219.40   $219.40  
  Purchase #5 $222.94   10.310%   $245.9251   $245.93   $245.95   $245.90  
  Purchase #6 $165.72   4.755%   $173.6   $173.60   $173.60   $173.60  
  Purchase #7 $181.76   8.706%   $197.584   $197.58   $197.60   $197.60  
  7 purchase totals = $1,200.62       $1,297.0482   $1,297.05   $1,297.10   $1,297.10