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 $55.44   11.816%   $61.9908   $61.99   $62.00   $62.00  
  Purchase #2 $161.85   4.295%   $168.8015   $168.80   $168.80   $168.80  
  Purchase #3 $222.33   5.460%   $234.4692   $234.47   $234.45   $234.50  
  Purchase #4 $171.84   12.680%   $193.6293   $193.63   $193.65   $193.60  
  Purchase #5 $196.68   8.737%   $213.8639   $213.86   $213.85   $213.90  
  Purchase #6 $35.89   5.702%   $37.9364   $37.94   $37.95   $37.90  
  Purchase #7 $115.40   6.797%   $123.2437   $123.24   $123.25   $123.20  
  7 purchase totals = $959.43       $1,033.9348   $1,033.93   $1,033.95   $1,033.90