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 $151.64   7.271%   $162.6657   $162.67   $162.65   $162.70  
  Purchase #2 $172.39   12.205%   $193.4302   $193.43   $193.45   $193.40  
  Purchase #3 $90.55   4.676%   $94.7841   $94.78   $94.80   $94.80  
  Purchase #4 $150.40   3.266%   $155.3121   $155.31   $155.30   $155.30  
  Purchase #5 $23.50   12.827%   $26.5143   $26.51   $26.50   $26.50  
  Purchase #6 $240.25   5.177%   $252.6877   $252.69   $252.70   $252.70  
  Purchase #7 $67.89   12.838%   $76.6057   $76.61   $76.60   $76.60  
  7 purchase totals = $896.62       $961.9998   $962.00   $962.00   $962.00