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 $186.51   10.271%   $205.6664   $205.67   $205.65   $205.70  
  Purchase #2 $191.96   11.555%   $214.141   $214.14   $214.15   $214.10  
  Purchase #3 $69.93   3.840%   $72.6153   $72.62   $72.60   $72.60  
  Purchase #4 $44.40   9.788%   $48.7459   $48.75   $48.75   $48.70  
  Purchase #5 $72.68   5.689%   $76.8148   $76.81   $76.80   $76.80  
  Purchase #6 $14.56   7.129%   $15.598   $15.60   $15.60   $15.60  
  Purchase #7 $219.48   3.751%   $227.7127   $227.71   $227.70   $227.70  
  7 purchase totals = $799.52       $861.2941   $861.30   $861.25   $861.20