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 $68.86   12.685%   $77.5949   $77.59   $77.60   $77.60  
  Purchase #2 $133.25   13.816%   $151.6598   $151.66   $151.65   $151.70  
  Purchase #3 $229.25   12.211%   $257.2437   $257.24   $257.25   $257.20  
  Purchase #4 $237.76   10.445%   $262.594   $262.59   $262.60   $262.60  
  Purchase #5 $114.89   9.329%   $125.6081   $125.61   $125.60   $125.60  
  Purchase #6 $108.88   8.230%   $117.8408   $117.84   $117.85   $117.80  
  Purchase #7 $111.66   11.321%   $124.301   $124.30   $124.30   $124.30  
  7 purchase totals = $1,004.55       $1,116.8423   $1,116.83   $1,116.85   $1,116.80