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 $52.82   11.832%   $59.0697   $59.07   $59.05   $59.10  
  Purchase #2 $196.67   4.613%   $205.7424   $205.74   $205.75   $205.70  
  Purchase #3 $187.76   10.788%   $208.0155   $208.02   $208.00   $208.00  
  Purchase #4 $50.99   10.670%   $56.4306   $56.43   $56.45   $56.40  
  Purchase #5 $199.79   8.616%   $217.0039   $217.00   $217.00   $217.00  
  Purchase #6 $55.35   4.338%   $57.7511   $57.75   $57.75   $57.80  
  Purchase #7 $195.29   5.711%   $206.443   $206.44   $206.45   $206.40  
  7 purchase totals = $938.67       $1,010.4562   $1,010.45   $1,010.45   $1,010.40