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 $91.63   4.394%   $95.6562   $95.66   $95.65   $95.70  
  Purchase #2 $224.71   13.250%   $254.4841   $254.48   $254.50   $254.50  
  Purchase #3 $126.92   3.797%   $131.7392   $131.74   $131.75   $131.70  
  Purchase #4 $200.66   13.376%   $227.5003   $227.50   $227.50   $227.50  
  Purchase #5 $108.36   9.195%   $118.3237   $118.32   $118.30   $118.30  
  Purchase #6 $71.53   3.498%   $74.0321   $74.03   $74.05   $74.00  
  Purchase #7 $59.27   10.389%   $65.4276   $65.43   $65.45   $65.40  
  7 purchase totals = $883.08       $967.1632   $967.16   $967.20   $967.10