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 $224.44   7.451%   $241.163   $241.16   $241.15   $241.20  
  Purchase #2 $236.78   13.733%   $269.297   $269.30   $269.30   $269.30  
  Purchase #3 $43.44   3.305%   $44.8757   $44.88   $44.90   $44.90  
  Purchase #4 $50.33   5.423%   $53.0594   $53.06   $53.05   $53.10  
  Purchase #5 $238.87   6.557%   $254.5327   $254.53   $254.55   $254.50  
  Purchase #6 $224.41   4.804%   $235.1907   $235.19   $235.20   $235.20  
  Purchase #7 $51.32   8.401%   $55.6314   $55.63   $55.65   $55.60  
  7 purchase totals = $1,069.59       $1,153.7499   $1,153.75   $1,153.80   $1,153.80