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 $114.25   10.546%   $126.2988   $126.30   $126.30   $126.30  
  Purchase #2 $186.90   11.795%   $208.9449   $208.94   $208.95   $208.90  
  Purchase #3 $187.65   10.670%   $207.6723   $207.67   $207.65   $207.70  
  Purchase #4 $119.79   12.370%   $134.608   $134.61   $134.60   $134.60  
  Purchase #5 $239.89   10.730%   $265.6302   $265.63   $265.65   $265.60  
  Purchase #6 $26.26   3.728%   $27.239   $27.24   $27.25   $27.20  
  Purchase #7 $171.72   3.539%   $177.7972   $177.80   $177.80   $177.80  
  7 purchase totals = $1,046.46       $1,148.1904   $1,148.19   $1,148.20   $1,148.10