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 $175.93   11.379%   $195.9491   $195.95   $195.95   $195.90  
  Purchase #2 $136.39   13.258%   $154.4726   $154.47   $154.45   $154.50  
  Purchase #3 $46.96   9.652%   $51.4926   $51.49   $51.50   $51.50  
  Purchase #4 $220.75   8.405%   $239.304   $239.30   $239.30   $239.30  
  Purchase #5 $248.30   8.658%   $269.7978   $269.80   $269.80   $269.80  
  Purchase #6 $157.62   8.834%   $171.5442   $171.54   $171.55   $171.50  
  Purchase #7 $137.28   5.859%   $145.3232   $145.32   $145.30   $145.30  
  7 purchase totals = $1,123.23       $1,227.8835   $1,227.87   $1,227.85   $1,227.80