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 $67.29   8.820%   $73.225   $73.23   $73.25   $73.20  
  Purchase #2 $24.49   4.473%   $25.5854   $25.59   $25.60   $25.60  
  Purchase #3 $139.46   6.554%   $148.6002   $148.60   $148.60   $148.60  
  Purchase #4 $173.72   6.591%   $185.1699   $185.17   $185.15   $185.20  
  Purchase #5 $224.68   13.827%   $255.7465   $255.75   $255.75   $255.70  
  Purchase #6 $246.27   6.312%   $261.8146   $261.81   $261.80   $261.80  
  Purchase #7 $172.85   11.656%   $192.9974   $193.00   $193.00   $193.00  
  7 purchase totals = $1,048.76       $1,143.1390   $1,143.15   $1,143.15   $1,143.10