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 $68.57   7.481%   $73.6997   $73.70   $73.70   $73.70  
  Purchase #2 $152.46   6.808%   $162.8395   $162.84   $162.85   $162.80  
  Purchase #3 $9.30   9.276%   $10.1627   $10.16   $10.15   $10.20  
  Purchase #4 $186.55   11.699%   $208.3745   $208.37   $208.35   $208.40  
  Purchase #5 $184.58   13.164%   $208.8781   $208.88   $208.90   $208.90  
  Purchase #6 $36.55   5.860%   $38.6918   $38.69   $38.70   $38.70  
  Purchase #7 $47.89   10.641%   $52.986   $52.99   $53.00   $53.00  
  7 purchase totals = $685.90       $755.6323   $755.63   $755.65   $755.70