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 $136.83   3.503%   $141.6232   $141.62   $141.60   $141.60  
  Purchase #2 $132.80   10.130%   $146.2526   $146.25   $146.25   $146.30  
  Purchase #3 $236.45   11.144%   $262.8   $262.80   $262.80   $262.80  
  Purchase #4 $41.88   13.643%   $47.5937   $47.59   $47.60   $47.60  
  Purchase #5 $229.62   8.256%   $248.5774   $248.58   $248.60   $248.60  
  Purchase #6 $211.84   7.726%   $228.2068   $228.21   $228.20   $228.20  
  Purchase #7 $24.55   7.748%   $26.4521   $26.45   $26.45   $26.50  
  7 purchase totals = $1,013.97       $1,101.5058   $1,101.50   $1,101.50   $1,101.60