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 $108.49   5.484%   $114.4396   $114.44   $114.45   $114.40  
  Purchase #2 $221.41   12.747%   $249.6331   $249.63   $249.65   $249.60  
  Purchase #3 $110.83   8.360%   $120.0954   $120.10   $120.10   $120.10  
  Purchase #4 $169.48   5.470%   $178.7506   $178.75   $178.75   $178.80  
  Purchase #5 $189.93   3.345%   $196.2832   $196.28   $196.30   $196.30  
  Purchase #6 $213.87   12.778%   $241.1983   $241.20   $241.20   $241.20  
  Purchase #7 $102.46   11.721%   $114.4693   $114.47   $114.45   $114.50  
  7 purchase totals = $1,116.47       $1,214.8695   $1,214.87   $1,214.90   $1,214.90