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 $205.61   4.541%   $214.9468   $214.95   $214.95   $214.90  
  Purchase #2 $44.54   3.470%   $46.0855   $46.09   $46.10   $46.10  
  Purchase #3 $166.55   10.455%   $183.9628   $183.96   $183.95   $184.00  
  Purchase #4 $240.92   9.154%   $262.9738   $262.97   $262.95   $263.00  
  Purchase #5 $34.68   3.508%   $35.8966   $35.90   $35.90   $35.90  
  Purchase #6 $182.88   4.478%   $191.0694   $191.07   $191.05   $191.10  
  Purchase #7 $23.37   13.865%   $26.6103   $26.61   $26.60   $26.60  
  7 purchase totals = $898.55       $961.5452   $961.55   $961.50   $961.60