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 $46.28   6.862%   $49.4557   $49.46   $49.45   $49.50  
  Purchase #2 $171.53   8.829%   $186.6744   $186.67   $186.65   $186.70  
  Purchase #3 $206.86   5.787%   $218.831   $218.83   $218.85   $218.80  
  Purchase #4 $49.49   13.589%   $56.2152   $56.22   $56.20   $56.20  
  Purchase #5 $200.96   12.692%   $226.4658   $226.47   $226.45   $226.50  
  Purchase #6 $190.80   8.507%   $207.0314   $207.03   $207.05   $207.00  
  Purchase #7 $214.71   11.151%   $238.6523   $238.65   $238.65   $238.70  
  7 purchase totals = $1,080.63       $1,183.3258   $1,183.33   $1,183.30   $1,183.40