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 $147.95   11.220%   $164.55   $164.55   $164.55   $164.60  
  Purchase #2 $146.93   4.841%   $154.0429   $154.04   $154.05   $154.00  
  Purchase #3 $39.61   12.323%   $44.4911   $44.49   $44.50   $44.50  
  Purchase #4 $126.25   9.236%   $137.9105   $137.91   $137.90   $137.90  
  Purchase #5 $185.83   12.414%   $208.8989   $208.90   $208.90   $208.90  
  Purchase #6 $166.76   3.564%   $172.7033   $172.70   $172.70   $172.70  
  Purchase #7 $63.96   9.490%   $70.0298   $70.03   $70.05   $70.00  
  7 purchase totals = $877.29       $952.6265   $952.62   $952.65   $952.60