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 $32.72   6.556%   $34.8651   $34.87   $34.85   $34.90  
  Purchase #2 $201.69   3.549%   $208.848   $208.85   $208.85   $208.80  
  Purchase #3 $20.66   8.400%   $22.3954   $22.40   $22.40   $22.40  
  Purchase #4 $162.75   6.543%   $173.3987   $173.40   $173.40   $173.40  
  Purchase #5 $193.73   5.391%   $204.174   $204.17   $204.15   $204.20  
  Purchase #6 $20.68   7.644%   $22.2608   $22.26   $22.25   $22.30  
  Purchase #7 $200.48   8.852%   $218.2265   $218.23   $218.25   $218.20  
  7 purchase totals = $832.71       $884.1685   $884.18   $884.15   $884.20