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 $203.57   11.289%   $226.551   $226.55   $226.55   $226.60  
  Purchase #2 $110.32   3.683%   $114.3831   $114.38   $114.40   $114.40  
  Purchase #3 $67.58   12.455%   $75.9971   $76.00   $76.00   $76.00  
  Purchase #4 $222.27   10.529%   $245.6728   $245.67   $245.65   $245.70  
  Purchase #5 $180.42   9.217%   $197.0493   $197.05   $197.05   $197.00  
  Purchase #6 $64.88   13.864%   $73.875   $73.88   $73.90   $73.90  
  Purchase #7 $105.41   5.280%   $110.9756   $110.98   $111.00   $111.00  
  7 purchase totals = $954.45       $1,044.5039   $1,044.51   $1,044.55   $1,044.60