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 $84.72   12.245%   $95.094   $95.09   $95.10   $95.10  
  Purchase #2 $235.84   12.500%   $265.32   $265.32   $265.30   $265.30  
  Purchase #3 $34.99   10.698%   $38.7332   $38.73   $38.75   $38.70  
  Purchase #4 $130.89   13.558%   $148.6361   $148.64   $148.65   $148.60  
  Purchase #5 $250.68   3.158%   $258.5965   $258.60   $258.60   $258.60  
  Purchase #6 $53.32   4.312%   $55.6192   $55.62   $55.60   $55.60  
  Purchase #7 $168.80   13.848%   $192.1754   $192.18   $192.20   $192.20  
  7 purchase totals = $959.24       $1,054.1744   $1,054.18   $1,054.20   $1,054.10