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 $70.78   8.737%   $76.964   $76.96   $76.95   $77.00  
  Purchase #2 $175.93   11.177%   $195.5937   $195.59   $195.60   $195.60  
  Purchase #3 $71.76   12.516%   $80.7415   $80.74   $80.75   $80.70  
  Purchase #4 $104.45   8.116%   $112.9272   $112.93   $112.95   $112.90  
  Purchase #5 $192.47   7.498%   $206.9014   $206.90   $206.90   $206.90  
  Purchase #6 $187.93   10.138%   $206.9823   $206.98   $207.00   $207.00  
  Purchase #7 $40.92   7.291%   $43.9035   $43.90   $43.90   $43.90  
  7 purchase totals = $844.24       $924.0136   $924.00   $924.05   $924.00