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 $44.65   5.852%   $47.2629   $47.26   $47.25   $47.30  
  Purchase #2 $118.85   4.723%   $124.4633   $124.46   $124.45   $124.50  
  Purchase #3 $182.88   8.490%   $198.4065   $198.41   $198.40   $198.40  
  Purchase #4 $192.63   8.262%   $208.5451   $208.55   $208.55   $208.50  
  Purchase #5 $201.73   8.338%   $218.5502   $218.55   $218.55   $218.60  
  Purchase #6 $120.50   11.576%   $134.4491   $134.45   $134.45   $134.40  
  Purchase #7 $127.96   3.125%   $131.9588   $131.96   $131.95   $132.00  
  7 purchase totals = $989.20       $1,063.6359   $1,063.64   $1,063.60   $1,063.70