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 $192.41   8.595%   $208.9476   $208.95   $208.95   $208.90  
  Purchase #2 $19.38   12.286%   $21.761   $21.76   $21.75   $21.80  
  Purchase #3 $207.41   3.361%   $214.3811   $214.38   $214.40   $214.40  
  Purchase #4 $209.42   12.429%   $235.4488   $235.45   $235.45   $235.40  
  Purchase #5 $57.94   12.116%   $64.96   $64.96   $64.95   $65.00  
  Purchase #6 $194.69   4.730%   $203.8988   $203.90   $203.90   $203.90  
  Purchase #7 $198.91   9.370%   $217.5479   $217.55   $217.55   $217.50  
  7 purchase totals = $1,080.16       $1,166.9452   $1,166.95   $1,166.95   $1,166.90