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 $69.65   10.479%   $76.9486   $76.95   $76.95   $76.90  
  Purchase #2 $12.43   7.616%   $13.3767   $13.38   $13.40   $13.40  
  Purchase #3 $182.32   9.403%   $199.4635   $199.46   $199.45   $199.50  
  Purchase #4 $47.69   3.577%   $49.3959   $49.40   $49.40   $49.40  
  Purchase #5 $192.74   5.745%   $203.8129   $203.81   $203.80   $203.80  
  Purchase #6 $174.50   6.706%   $186.202   $186.20   $186.20   $186.20  
  Purchase #7 $27.52   11.742%   $30.7514   $30.75   $30.75   $30.80  
  7 purchase totals = $706.85       $759.9510   $759.95   $759.95   $760.00