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 $24.38   6.760%   $26.0281   $26.03   $26.05   $26.00  
  Purchase #2 $16.91   5.597%   $17.8565   $17.86   $17.85   $17.90  
  Purchase #3 $29.68   11.491%   $33.0905   $33.09   $33.10   $33.10  
  Purchase #4 $177.32   10.225%   $195.451   $195.45   $195.45   $195.50  
  Purchase #5 $143.45   8.679%   $155.9   $155.90   $155.90   $155.90  
  Purchase #6 $142.90   8.454%   $154.9808   $154.98   $155.00   $155.00  
  Purchase #7 $161.84   6.453%   $172.2835   $172.28   $172.30   $172.30  
  7 purchase totals = $696.48       $755.5904   $755.59   $755.65   $755.70