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 $153.66   10.328%   $169.53   $169.53   $169.55   $169.50  
  Purchase #2 $239.68   11.794%   $267.9479   $267.95   $267.95   $267.90  
  Purchase #3 $56.44   12.428%   $63.4544   $63.45   $63.45   $63.50  
  Purchase #4 $222.74   3.302%   $230.0949   $230.09   $230.10   $230.10  
  Purchase #5 $41.31   7.497%   $44.407   $44.41   $44.40   $44.40  
  Purchase #6 $101.38   6.735%   $108.2079   $108.21   $108.20   $108.20  
  Purchase #7 $217.83   4.468%   $227.5626   $227.56   $227.55   $227.60  
  7 purchase totals = $1,033.04       $1,111.2047   $1,111.20   $1,111.20   $1,111.20