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 $163.84   11.467%   $182.6275   $182.63   $182.65   $182.60  
  Purchase #2 $136.44   11.378%   $151.9641   $151.96   $151.95   $152.00  
  Purchase #3 $61.44   3.337%   $63.4903   $63.49   $63.50   $63.50  
  Purchase #4 $182.87   9.195%   $199.6849   $199.68   $199.70   $199.70  
  Purchase #5 $198.80   4.677%   $208.0979   $208.10   $208.10   $208.10  
  Purchase #6 $194.68   11.335%   $216.747   $216.75   $216.75   $216.70  
  Purchase #7 $16.48   11.151%   $18.3177   $18.32   $18.30   $18.30  
  7 purchase totals = $954.55       $1,040.9294   $1,040.93   $1,040.95   $1,040.90