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 $214.43   10.204%   $236.3104   $236.31   $236.30   $236.30  
  Purchase #2 $228.98   8.422%   $248.2647   $248.26   $248.25   $248.30  
  Purchase #3 $186.99   4.419%   $195.2531   $195.25   $195.25   $195.30  
  Purchase #4 $48.55   8.266%   $52.5631   $52.56   $52.55   $52.60  
  Purchase #5 $106.48   3.665%   $110.3825   $110.38   $110.40   $110.40  
  Purchase #6 $170.31   5.529%   $179.7264   $179.73   $179.75   $179.70  
  Purchase #7 $118.76   6.315%   $126.2597   $126.26   $126.25   $126.30  
  7 purchase totals = $1,074.50       $1,148.7599   $1,148.75   $1,148.75   $1,148.90