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 $181.74   13.630%   $206.5112   $206.51   $206.50   $206.50  
  Purchase #2 $195.75   8.116%   $211.6371   $211.64   $211.65   $211.60  
  Purchase #3 $176.25   9.541%   $193.066   $193.07   $193.05   $193.10  
  Purchase #4 $104.72   10.758%   $115.9858   $115.99   $116.00   $116.00  
  Purchase #5 $133.74   8.603%   $145.2457   $145.25   $145.25   $145.20  
  Purchase #6 $88.76   8.752%   $96.5283   $96.53   $96.55   $96.50  
  Purchase #7 $217.71   8.241%   $235.6515   $235.65   $235.65   $235.70  
  7 purchase totals = $1,098.67       $1,204.6256   $1,204.64   $1,204.65   $1,204.60