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 $120.64   5.485%   $127.2571   $127.26   $127.25   $127.30  
  Purchase #2 $123.73   10.247%   $136.4086   $136.41   $136.40   $136.40  
  Purchase #3 $118.31   11.678%   $132.1262   $132.13   $132.15   $132.10  
  Purchase #4 $32.58   5.369%   $34.3292   $34.33   $34.35   $34.30  
  Purchase #5 $51.86   6.446%   $55.2029   $55.20   $55.20   $55.20  
  Purchase #6 $205.92   6.611%   $219.5334   $219.53   $219.55   $219.50  
  Purchase #7 $248.59   5.239%   $261.6136   $261.61   $261.60   $261.60  
  7 purchase totals = $901.63       $966.4710   $966.47   $966.50   $966.40