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 $41.42   5.269%   $43.6024   $43.60   $43.60   $43.60  
  Purchase #2 $15.29   4.394%   $15.9618   $15.96   $15.95   $16.00  
  Purchase #3 $180.46   6.472%   $192.1394   $192.14   $192.15   $192.10  
  Purchase #4 $213.72   8.608%   $232.117   $232.12   $232.10   $232.10  
  Purchase #5 $223.57   3.720%   $231.8868   $231.89   $231.90   $231.90  
  Purchase #6 $217.58   4.148%   $226.6052   $226.61   $226.60   $226.60  
  Purchase #7 $76.81   12.747%   $86.601   $86.60   $86.60   $86.60  
  7 purchase totals = $968.85       $1,028.9136   $1,028.92   $1,028.90   $1,028.90