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 $185.76   5.824%   $196.5787   $196.58   $196.60   $196.60  
  Purchase #2 $222.57   4.747%   $233.1354   $233.14   $233.15   $233.10  
  Purchase #3 $184.47   12.149%   $206.8813   $206.88   $206.90   $206.90  
  Purchase #4 $144.66   11.732%   $161.6315   $161.63   $161.65   $161.60  
  Purchase #5 $198.55   6.300%   $211.0587   $211.06   $211.05   $211.10  
  Purchase #6 $221.81   11.763%   $247.9015   $247.90   $247.90   $247.90  
  Purchase #7 $86.98   9.105%   $94.8995   $94.90   $94.90   $94.90  
  7 purchase totals = $1,244.80       $1,352.0866   $1,352.09   $1,352.15   $1,352.10