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 $227.62   6.186%   $241.7006   $241.70   $241.70   $241.70  
  Purchase #2 $68.84   7.595%   $74.0684   $74.07   $74.05   $74.10  
  Purchase #3 $65.26   7.533%   $70.176   $70.18   $70.20   $70.20  
  Purchase #4 $201.41   3.450%   $208.3586   $208.36   $208.35   $208.40  
  Purchase #5 $187.28   9.685%   $205.4181   $205.42   $205.40   $205.40  
  Purchase #6 $248.97   4.733%   $260.7538   $260.75   $260.75   $260.80  
  Purchase #7 $162.49   7.710%   $175.018   $175.02   $175.00   $175.00  
  7 purchase totals = $1,161.87       $1,235.4935   $1,235.50   $1,235.45   $1,235.60