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 $208.87   3.661%   $216.5167   $216.52   $216.50   $216.50  
  Purchase #2 $226.59   10.566%   $250.5315   $250.53   $250.55   $250.50  
  Purchase #3 $239.60   8.207%   $259.264   $259.26   $259.25   $259.30  
  Purchase #4 $76.69   7.247%   $82.2477   $82.25   $82.25   $82.20  
  Purchase #5 $131.49   9.848%   $144.4391   $144.44   $144.45   $144.40  
  Purchase #6 $183.87   11.169%   $204.4064   $204.41   $204.40   $204.40  
  Purchase #7 $189.80   7.464%   $203.9667   $203.97   $203.95   $204.00  
  7 purchase totals = $1,256.91       $1,361.3721   $1,361.38   $1,361.35   $1,361.30