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 $57.86   12.715%   $65.2169   $65.22   $65.20   $65.20  
  Purchase #2 $190.64   9.137%   $208.0588   $208.06   $208.05   $208.10  
  Purchase #3 $246.98   6.359%   $262.6855   $262.69   $262.70   $262.70  
  Purchase #4 $205.91   3.429%   $212.9707   $212.97   $212.95   $213.00  
  Purchase #5 $45.33   5.661%   $47.8961   $47.90   $47.90   $47.90  
  Purchase #6 $168.80   11.491%   $188.1968   $188.20   $188.20   $188.20  
  Purchase #7 $131.69   5.822%   $139.357   $139.36   $139.35   $139.40  
  7 purchase totals = $1,047.21       $1,124.3818   $1,124.40   $1,124.35   $1,124.50