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 $59.49   3.623%   $61.6453   $61.65   $61.65   $61.60  
  Purchase #2 $214.65   11.123%   $238.5255   $238.53   $238.55   $238.50  
  Purchase #3 $237.70   6.189%   $252.4113   $252.41   $252.40   $252.40  
  Purchase #4 $145.63   5.406%   $153.5028   $153.50   $153.50   $153.50  
  Purchase #5 $215.30   12.670%   $242.5785   $242.58   $242.60   $242.60  
  Purchase #6 $120.39   3.509%   $124.6145   $124.61   $124.60   $124.60  
  Purchase #7 $156.47   9.661%   $171.5866   $171.59   $171.60   $171.60  
  7 purchase totals = $1,149.63       $1,244.8645   $1,244.87   $1,244.90   $1,244.80