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 $86.62   9.688%   $95.0117   $95.01   $95.00   $95.00  
  Purchase #2 $74.68   7.509%   $80.2877   $80.29   $80.30   $80.30  
  Purchase #3 $233.70   13.418%   $265.0579   $265.06   $265.05   $265.10  
  Purchase #4 $179.83   9.874%   $197.5864   $197.59   $197.60   $197.60  
  Purchase #5 $49.62   6.365%   $52.7783   $52.78   $52.80   $52.80  
  Purchase #6 $52.60   7.436%   $56.5113   $56.51   $56.50   $56.50  
  Purchase #7 $221.51   7.336%   $237.76   $237.76   $237.75   $237.80  
  7 purchase totals = $898.56       $984.9933   $985.00   $985.00   $985.10