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 $214.87   5.855%   $227.4506   $227.45   $227.45   $227.50  
  Purchase #2 $202.53   10.546%   $223.8888   $223.89   $223.90   $223.90  
  Purchase #3 $6.45   3.119%   $6.6512   $6.65   $6.65   $6.70  
  Purchase #4 $239.39   13.277%   $271.1738   $271.17   $271.15   $271.20  
  Purchase #5 $44.85   4.177%   $46.7234   $46.72   $46.70   $46.70  
  Purchase #6 $169.75   7.300%   $182.1418   $182.14   $182.15   $182.10  
  Purchase #7 $198.75   7.807%   $214.2664   $214.27   $214.25   $214.30  
  7 purchase totals = $1,076.59       $1,172.2960   $1,172.29   $1,172.25   $1,172.40