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 $212.73   6.253%   $226.032   $226.03   $226.05   $226.00  
  Purchase #2 $114.28   10.589%   $126.3811   $126.38   $126.40   $126.40  
  Purchase #3 $166.86   8.522%   $181.0798   $181.08   $181.10   $181.10  
  Purchase #4 $190.33   3.284%   $196.5804   $196.58   $196.60   $196.60  
  Purchase #5 $26.62   7.680%   $28.6644   $28.66   $28.65   $28.70  
  Purchase #6 $23.70   10.140%   $26.1032   $26.10   $26.10   $26.10  
  Purchase #7 $118.78   11.116%   $131.9836   $131.98   $132.00   $132.00  
  7 purchase totals = $853.30       $916.8245   $916.81   $916.90   $916.90