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 $232.62   13.215%   $263.3607   $263.36   $263.35   $263.40  
  Purchase #2 $53.26   11.234%   $59.2432   $59.24   $59.25   $59.20  
  Purchase #3 $34.49   10.724%   $38.1887   $38.19   $38.20   $38.20  
  Purchase #4 $52.55   8.258%   $56.8896   $56.89   $56.90   $56.90  
  Purchase #5 $250.30   5.132%   $263.1454   $263.15   $263.15   $263.10  
  Purchase #6 $181.43   8.629%   $197.0856   $197.09   $197.10   $197.10  
  Purchase #7 $165.28   7.132%   $177.0678   $177.07   $177.05   $177.10  
  7 purchase totals = $969.93       $1,054.9810   $1,054.99   $1,055.00   $1,055.00