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 $198.54   4.745%   $207.9607   $207.96   $207.95   $208.00  
  Purchase #2 $88.81   4.120%   $92.469   $92.47   $92.45   $92.50  
  Purchase #3 $70.72   8.284%   $76.5784   $76.58   $76.60   $76.60  
  Purchase #4 $198.63   3.376%   $205.3357   $205.34   $205.35   $205.30  
  Purchase #5 $126.29   8.285%   $136.7531   $136.75   $136.75   $136.80  
  Purchase #6 $123.66   5.505%   $130.4675   $130.47   $130.45   $130.50  
  Purchase #7 $212.63   4.738%   $222.7044   $222.70   $222.70   $222.70  
  7 purchase totals = $1,019.28       $1,072.2688   $1,072.27   $1,072.25   $1,072.40