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 $33.48   4.762%   $35.0743   $35.07   $35.05   $35.10  
  Purchase #2 $136.58   3.871%   $141.867   $141.87   $141.85   $141.90  
  Purchase #3 $129.82   10.589%   $143.5666   $143.57   $143.55   $143.60  
  Purchase #4 $101.67   8.194%   $110.0008   $110.00   $110.00   $110.00  
  Purchase #5 $212.37   11.641%   $237.092   $237.09   $237.10   $237.10  
  Purchase #6 $169.87   7.717%   $182.9789   $182.98   $183.00   $183.00  
  Purchase #7 $179.67   7.756%   $193.6052   $193.61   $193.60   $193.60  
  7 purchase totals = $963.46       $1,044.1848   $1,044.19   $1,044.15   $1,044.30