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 $101.96   12.636%   $114.8437   $114.84   $114.85   $114.80  
  Purchase #2 $234.93   8.221%   $254.2436   $254.24   $254.25   $254.20  
  Purchase #3 $101.85   11.405%   $113.466   $113.47   $113.45   $113.50  
  Purchase #4 $236.39   9.726%   $259.3813   $259.38   $259.40   $259.40  
  Purchase #5 $195.25   10.420%   $215.5951   $215.60   $215.60   $215.60  
  Purchase #6 $223.58   13.839%   $254.5212   $254.52   $254.50   $254.50  
  Purchase #7 $170.99   7.139%   $183.197   $183.20   $183.20   $183.20  
  7 purchase totals = $1,264.95       $1,395.2479   $1,395.25   $1,395.25   $1,395.20