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 $248.26   8.633%   $269.6923   $269.69   $269.70   $269.70  
  Purchase #2 $134.80   5.379%   $142.0509   $142.05   $142.05   $142.10  
  Purchase #3 $186.99   4.575%   $195.5448   $195.54   $195.55   $195.50  
  Purchase #4 $61.85   9.260%   $67.5773   $67.58   $67.60   $67.60  
  Purchase #5 $78.87   11.671%   $88.0749   $88.07   $88.05   $88.10  
  Purchase #6 $218.89   7.210%   $234.672   $234.67   $234.65   $234.70  
  Purchase #7 $174.37   10.366%   $192.4452   $192.45   $192.45   $192.40  
  7 purchase totals = $1,104.03       $1,190.0574   $1,190.05   $1,190.05   $1,190.10