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 $89.64   6.570%   $95.5293   $95.53   $95.55   $95.50  
  Purchase #2 $200.34   3.163%   $206.6768   $206.68   $206.70   $206.70  
  Purchase #3 $248.64   7.307%   $266.8081   $266.81   $266.80   $266.80  
  Purchase #4 $51.28   8.458%   $55.6173   $55.62   $55.60   $55.60  
  Purchase #5 $179.40   11.843%   $200.6463   $200.65   $200.65   $200.60  
  Purchase #6 $171.83   9.561%   $188.2587   $188.26   $188.25   $188.30  
  Purchase #7 $234.63   11.688%   $262.0536   $262.05   $262.05   $262.10  
  7 purchase totals = $1,175.76       $1,275.5901   $1,275.60   $1,275.60   $1,275.60