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 $226.41   4.212%   $235.9464   $235.95   $235.95   $235.90  
  Purchase #2 $98.42   4.849%   $103.1924   $103.19   $103.20   $103.20  
  Purchase #3 $140.57   10.759%   $155.6939   $155.69   $155.70   $155.70  
  Purchase #4 $246.50   12.119%   $276.3733   $276.37   $276.35   $276.40  
  Purchase #5 $94.58   3.259%   $97.6624   $97.66   $97.65   $97.70  
  Purchase #6 $90.34   12.108%   $101.2784   $101.28   $101.30   $101.30  
  Purchase #7 $125.82   6.725%   $134.2814   $134.28   $134.30   $134.30  
  7 purchase totals = $1,022.64       $1,104.4282   $1,104.42   $1,104.45   $1,104.50