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 $68.76   5.557%   $72.581   $72.58   $72.60   $72.60  
  Purchase #2 $102.41   3.766%   $106.2668   $106.27   $106.25   $106.30  
  Purchase #3 $105.67   8.172%   $114.3054   $114.31   $114.30   $114.30  
  Purchase #4 $148.34   3.770%   $153.9324   $153.93   $153.95   $153.90  
  Purchase #5 $192.92   12.299%   $216.6472   $216.65   $216.65   $216.60  
  Purchase #6 $239.55   5.769%   $253.3696   $253.37   $253.35   $253.40  
  Purchase #7 $27.26   9.766%   $29.9222   $29.92   $29.90   $29.90  
  7 purchase totals = $884.91       $947.0246   $947.03   $947.00   $947.00