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 $102.72   11.114%   $114.1363   $114.14   $114.15   $114.10  
  Purchase #2 $245.46   8.534%   $266.4076   $266.41   $266.40   $266.40  
  Purchase #3 $157.64   4.501%   $164.7354   $164.74   $164.75   $164.70  
  Purchase #4 $72.59   9.280%   $79.3264   $79.33   $79.35   $79.30  
  Purchase #5 $141.77   10.423%   $156.5467   $156.55   $156.55   $156.50  
  Purchase #6 $84.79   4.537%   $88.6369   $88.64   $88.65   $88.60  
  Purchase #7 $218.43   6.136%   $231.8329   $231.83   $231.85   $231.80  
  7 purchase totals = $1,023.40       $1,101.6222   $1,101.64   $1,101.70   $1,101.40