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 $192.91   7.825%   $208.0052   $208.01   $208.00   $208.00  
  Purchase #2 $133.91   3.704%   $138.87   $138.87   $138.85   $138.90  
  Purchase #3 $186.51   7.508%   $200.5132   $200.51   $200.50   $200.50  
  Purchase #4 $202.93   8.746%   $220.6783   $220.68   $220.70   $220.70  
  Purchase #5 $83.46   11.692%   $93.2181   $93.22   $93.20   $93.20  
  Purchase #6 $75.53   8.471%   $81.9281   $81.93   $81.95   $81.90  
  Purchase #7 $22.38   6.409%   $23.8143   $23.81   $23.80   $23.80  
  7 purchase totals = $897.63       $967.0272   $967.03   $967.00   $967.00