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 $169.89   7.474%   $182.5876   $182.59   $182.60   $182.60  
  Purchase #2 $49.76   9.296%   $54.3857   $54.39   $54.40   $54.40  
  Purchase #3 $99.61   3.609%   $103.2049   $103.20   $103.20   $103.20  
  Purchase #4 $114.54   4.104%   $119.2407   $119.24   $119.25   $119.20  
  Purchase #5 $124.36   3.772%   $129.0509   $129.05   $129.05   $129.10  
  Purchase #6 $206.48   9.170%   $225.4142   $225.41   $225.40   $225.40  
  Purchase #7 $186.45   13.209%   $211.0782   $211.08   $211.10   $211.10  
  7 purchase totals = $951.09       $1,024.9622   $1,024.96   $1,025.00   $1,025.00