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 $108.89   5.515%   $114.8953   $114.90   $114.90   $114.90  
  Purchase #2 $41.79   10.794%   $46.3008   $46.30   $46.30   $46.30  
  Purchase #3 $226.92   9.661%   $248.8427   $248.84   $248.85   $248.80  
  Purchase #4 $116.59   4.851%   $122.2458   $122.25   $122.25   $122.20  
  Purchase #5 $248.58   7.129%   $266.3013   $266.30   $266.30   $266.30  
  Purchase #6 $248.77   9.560%   $272.5524   $272.55   $272.55   $272.60  
  Purchase #7 $214.74   8.582%   $233.169   $233.17   $233.15   $233.20  
  7 purchase totals = $1,206.28       $1,304.3073   $1,304.31   $1,304.30   $1,304.30