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 $85.41   8.466%   $92.6408   $92.64   $92.65   $92.60  
  Purchase #2 $84.69   13.445%   $96.0766   $96.08   $96.10   $96.10  
  Purchase #3 $246.77   10.606%   $272.9424   $272.94   $272.95   $272.90  
  Purchase #4 $234.50   7.238%   $251.4731   $251.47   $251.45   $251.50  
  Purchase #5 $242.68   11.127%   $269.683   $269.68   $269.70   $269.70  
  Purchase #6 $137.38   9.455%   $150.3693   $150.37   $150.35   $150.40  
  Purchase #7 $248.93   5.116%   $261.6653   $261.67   $261.65   $261.70  
  7 purchase totals = $1,280.36       $1,394.8505   $1,394.85   $1,394.85   $1,394.90