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 $218.27   8.242%   $236.2598   $236.26   $236.25   $236.30  
  Purchase #2 $190.48   13.728%   $216.6291   $216.63   $216.65   $216.60  
  Purchase #3 $39.70   9.857%   $43.6132   $43.61   $43.60   $43.60  
  Purchase #4 $114.45   11.437%   $127.5396   $127.54   $127.55   $127.50  
  Purchase #5 $64.42   6.627%   $68.6891   $68.69   $68.70   $68.70  
  Purchase #6 $219.27   3.211%   $226.3108   $226.31   $226.30   $226.30  
  Purchase #7 $193.53   11.674%   $216.1227   $216.12   $216.10   $216.10  
  7 purchase totals = $1,040.12       $1,135.1643   $1,135.16   $1,135.15   $1,135.10