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 $60.87   8.868%   $66.268   $66.27   $66.25   $66.30  
  Purchase #2 $143.84   12.716%   $162.1307   $162.13   $162.15   $162.10  
  Purchase #3 $119.81   10.803%   $132.7531   $132.75   $132.75   $132.80  
  Purchase #4 $49.97   4.182%   $52.0597   $52.06   $52.05   $52.10  
  Purchase #5 $66.46   5.249%   $69.9485   $69.95   $69.95   $69.90  
  Purchase #6 $48.80   8.821%   $53.1046   $53.10   $53.10   $53.10  
  Purchase #7 $184.76   5.551%   $195.016   $195.02   $195.00   $195.00  
  7 purchase totals = $674.51       $731.2806   $731.28   $731.25   $731.30