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 $57.79   10.418%   $63.8106   $63.81   $63.80   $63.80  
  Purchase #2 $32.88   4.564%   $34.3806   $34.38   $34.40   $34.40  
  Purchase #3 $212.32   11.187%   $236.0722   $236.07   $236.05   $236.10  
  Purchase #4 $155.33   3.586%   $160.9001   $160.90   $160.90   $160.90  
  Purchase #5 $200.32   8.341%   $217.0287   $217.03   $217.05   $217.00  
  Purchase #6 $192.53   13.479%   $218.4811   $218.48   $218.50   $218.50  
  Purchase #7 $168.61   8.328%   $182.6518   $182.65   $182.65   $182.70  
  7 purchase totals = $1,019.78       $1,113.3251   $1,113.32   $1,113.35   $1,113.40