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 $222.33   5.326%   $234.1713   $234.17   $234.15   $234.20  
  Purchase #2 $177.57   4.524%   $185.6033   $185.60   $185.60   $185.60  
  Purchase #3 $151.90   13.609%   $172.5721   $172.57   $172.55   $172.60  
  Purchase #4 $50.80   5.454%   $53.5706   $53.57   $53.55   $53.60  
  Purchase #5 $17.98   4.327%   $18.758   $18.76   $18.75   $18.80  
  Purchase #6 $77.63   5.532%   $81.9245   $81.92   $81.90   $81.90  
  Purchase #7 $20.25   13.732%   $23.0307   $23.03   $23.05   $23.00  
  7 purchase totals = $718.46       $769.6305   $769.62   $769.55   $769.70