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 $119.92   5.600%   $126.6355   $126.64   $126.65   $126.60  
  Purchase #2 $86.99   11.215%   $96.7459   $96.75   $96.75   $96.70  
  Purchase #3 $222.78   4.369%   $232.5133   $232.51   $232.50   $232.50  
  Purchase #4 $184.30   4.441%   $192.4848   $192.48   $192.50   $192.50  
  Purchase #5 $213.71   3.677%   $221.5681   $221.57   $221.55   $221.60  
  Purchase #6 $130.73   12.837%   $147.5118   $147.51   $147.50   $147.50  
  Purchase #7 $113.63   9.367%   $124.2737   $124.27   $124.25   $124.30  
  7 purchase totals = $1,072.06       $1,141.7331   $1,141.73   $1,141.70   $1,141.70