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 $54.38   12.659%   $61.264   $61.26   $61.25   $61.30  
  Purchase #2 $226.91   3.759%   $235.4395   $235.44   $235.45   $235.40  
  Purchase #3 $177.93   4.217%   $185.4333   $185.43   $185.45   $185.40  
  Purchase #4 $141.74   7.679%   $152.6242   $152.62   $152.60   $152.60  
  Purchase #5 $109.95   3.788%   $114.1149   $114.11   $114.10   $114.10  
  Purchase #6 $168.27   4.241%   $175.4063   $175.41   $175.40   $175.40  
  Purchase #7 $180.40   12.564%   $203.0655   $203.07   $203.05   $203.10  
  7 purchase totals = $1,059.58       $1,127.3477   $1,127.34   $1,127.30   $1,127.30