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 $232.67   13.569%   $264.241   $264.24   $264.25   $264.20  
  Purchase #2 $109.62   8.554%   $118.9969   $119.00   $119.00   $119.00  
  Purchase #3 $79.66   3.659%   $82.5748   $82.57   $82.55   $82.60  
  Purchase #4 $158.83   7.135%   $170.1625   $170.16   $170.15   $170.20  
  Purchase #5 $146.99   11.192%   $163.4411   $163.44   $163.45   $163.40  
  Purchase #6 $157.56   6.495%   $167.7935   $167.79   $167.80   $167.80  
  Purchase #7 $151.32   11.622%   $168.9064   $168.91   $168.90   $168.90  
  7 purchase totals = $1,036.65       $1,136.1162   $1,136.11   $1,136.10   $1,136.10