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 $59.54   4.428%   $62.1764   $62.18   $62.20   $62.20  
  Purchase #2 $136.69   12.325%   $153.537   $153.54   $153.55   $153.50  
  Purchase #3 $225.71   10.405%   $249.1951   $249.20   $249.20   $249.20  
  Purchase #4 $57.51   3.223%   $59.3635   $59.36   $59.35   $59.40  
  Purchase #5 $201.68   12.423%   $226.7347   $226.73   $226.75   $226.70  
  Purchase #6 $97.79   6.477%   $104.1239   $104.12   $104.10   $104.10  
  Purchase #7 $179.51   10.815%   $198.924   $198.92   $198.90   $198.90  
  7 purchase totals = $958.43       $1,054.0546   $1,054.05   $1,054.05   $1,054.00