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 $46.99   3.332%   $48.5557   $48.56   $48.55   $48.60  
  Purchase #2 $224.47   8.228%   $242.9394   $242.94   $242.95   $242.90  
  Purchase #3 $188.99   3.638%   $195.8655   $195.87   $195.85   $195.90  
  Purchase #4 $66.55   10.723%   $73.6862   $73.69   $73.70   $73.70  
  Purchase #5 $109.80   12.256%   $123.2571   $123.26   $123.25   $123.30  
  Purchase #6 $171.63   10.241%   $189.2066   $189.21   $189.20   $189.20  
  Purchase #7 $168.51   10.235%   $185.757   $185.76   $185.75   $185.80  
  7 purchase totals = $976.94       $1,059.2675   $1,059.29   $1,059.25   $1,059.40