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 $72.83   5.379%   $76.7475   $76.75   $76.75   $76.70  
  Purchase #2 $113.81   10.255%   $125.4812   $125.48   $125.50   $125.50  
  Purchase #3 $193.48   5.486%   $204.0943   $204.09   $204.10   $204.10  
  Purchase #4 $124.87   7.687%   $134.4688   $134.47   $134.45   $134.50  
  Purchase #5 $115.65   10.585%   $127.8916   $127.89   $127.90   $127.90  
  Purchase #6 $45.90   4.257%   $47.854   $47.85   $47.85   $47.90  
  Purchase #7 $221.32   6.334%   $235.3384   $235.34   $235.35   $235.30  
  7 purchase totals = $887.86       $951.8758   $951.87   $951.90   $951.90