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 $235.27   4.396%   $245.6125   $245.61   $245.60   $245.60  
  Purchase #2 $162.93   8.758%   $177.1994   $177.20   $177.20   $177.20  
  Purchase #3 $136.46   9.757%   $149.7744   $149.77   $149.75   $149.80  
  Purchase #4 $233.88   10.844%   $259.2419   $259.24   $259.25   $259.20  
  Purchase #5 $210.57   6.405%   $224.057   $224.06   $224.05   $224.10  
  Purchase #6 $153.66   11.793%   $171.7811   $171.78   $171.80   $171.80  
  Purchase #7 $222.69   5.746%   $235.4858   $235.49   $235.50   $235.50  
  7 purchase totals = $1,355.46       $1,463.1521   $1,463.15   $1,463.15   $1,463.20