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 $41.51   11.236%   $46.1741   $46.17   $46.15   $46.20  
  Purchase #2 $185.99   9.547%   $203.7465   $203.75   $203.75   $203.70  
  Purchase #3 $217.70   10.739%   $241.0788   $241.08   $241.10   $241.10  
  Purchase #4 $27.96   9.725%   $30.6791   $30.68   $30.70   $30.70  
  Purchase #5 $72.77   6.636%   $77.599   $77.60   $77.60   $77.60  
  Purchase #6 $212.96   6.237%   $226.2423   $226.24   $226.25   $226.20  
  Purchase #7 $106.87   9.856%   $117.4031   $117.40   $117.40   $117.40  
  7 purchase totals = $865.76       $942.9229   $942.92   $942.95   $942.90