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 $114.94   10.839%   $127.3983   $127.40   $127.40   $127.40  
  Purchase #2 $107.37   7.376%   $115.2896   $115.29   $115.30   $115.30  
  Purchase #3 $164.43   13.499%   $186.6264   $186.63   $186.65   $186.60  
  Purchase #4 $192.79   6.851%   $205.998   $206.00   $206.00   $206.00  
  Purchase #5 $247.48   6.643%   $263.9201   $263.92   $263.90   $263.90  
  Purchase #6 $107.64   8.769%   $117.079   $117.08   $117.10   $117.10  
  Purchase #7 $128.88   13.210%   $145.905   $145.91   $145.90   $145.90  
  7 purchase totals = $1,063.53       $1,162.2164   $1,162.23   $1,162.25   $1,162.20