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 $95.29   11.591%   $106.3351   $106.34   $106.35   $106.30  
  Purchase #2 $127.81   7.554%   $137.4648   $137.46   $137.45   $137.50  
  Purchase #3 $230.34   13.344%   $261.0766   $261.08   $261.10   $261.10  
  Purchase #4 $241.61   11.194%   $268.6558   $268.66   $268.65   $268.70  
  Purchase #5 $165.33   11.244%   $183.9197   $183.92   $183.90   $183.90  
  Purchase #6 $194.66   7.329%   $208.9266   $208.93   $208.95   $208.90  
  Purchase #7 $86.53   8.705%   $94.0624   $94.06   $94.05   $94.10  
  7 purchase totals = $1,141.57       $1,260.4410   $1,260.45   $1,260.45   $1,260.50