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 $61.88   11.857%   $69.2171   $69.22   $69.20   $69.20  
  Purchase #2 $200.61   11.252%   $223.1826   $223.18   $223.20   $223.20  
  Purchase #3 $61.75   3.248%   $63.7556   $63.76   $63.75   $63.80  
  Purchase #4 $135.55   5.314%   $142.7531   $142.75   $142.75   $142.80  
  Purchase #5 $162.75   5.439%   $171.602   $171.60   $171.60   $171.60  
  Purchase #6 $186.56   6.231%   $198.1846   $198.18   $198.20   $198.20  
  Purchase #7 $62.49   7.718%   $67.313   $67.31   $67.30   $67.30  
  7 purchase totals = $871.59       $936.0080   $936.00   $936.00   $936.10