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 $206.37   5.691%   $218.1145   $218.11   $218.10   $218.10  
  Purchase #2 $228.37   3.663%   $236.7352   $236.74   $236.75   $236.70  
  Purchase #3 $76.77   12.520%   $86.3816   $86.38   $86.40   $86.40  
  Purchase #4 $212.48   11.670%   $237.2764   $237.28   $237.30   $237.30  
  Purchase #5 $48.99   11.428%   $54.5886   $54.59   $54.60   $54.60  
  Purchase #6 $43.88   6.525%   $46.7432   $46.74   $46.75   $46.70  
  Purchase #7 $167.48   9.494%   $183.3806   $183.38   $183.40   $183.40  
  7 purchase totals = $984.34       $1,063.2201   $1,063.22   $1,063.30   $1,063.20