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 $175.76   3.581%   $182.054   $182.05   $182.05   $182.10  
  Purchase #2 $124.71   4.727%   $130.605   $130.61   $130.60   $130.60  
  Purchase #3 $167.95   12.406%   $188.7859   $188.79   $188.80   $188.80  
  Purchase #4 $44.68   13.462%   $50.6948   $50.69   $50.70   $50.70  
  Purchase #5 $86.68   11.860%   $96.9602   $96.96   $96.95   $97.00  
  Purchase #6 $82.90   8.826%   $90.2168   $90.22   $90.20   $90.20  
  Purchase #7 $102.65   11.608%   $114.5656   $114.57   $114.55   $114.60  
  7 purchase totals = $785.33       $853.8823   $853.89   $853.85   $854.00