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 $68.94   10.329%   $76.0608   $76.06   $76.05   $76.10  
  Purchase #2 $37.68   4.190%   $39.2588   $39.26   $39.25   $39.30  
  Purchase #3 $83.26   3.103%   $85.8436   $85.84   $85.85   $85.80  
  Purchase #4 $164.65   5.636%   $173.9297   $173.93   $173.95   $173.90  
  Purchase #5 $105.93   7.669%   $114.0538   $114.05   $114.05   $114.10  
  Purchase #6 $201.97   9.741%   $221.6439   $221.64   $221.65   $221.60  
  Purchase #7 $233.30   8.563%   $253.2775   $253.28   $253.30   $253.30  
  7 purchase totals = $895.73       $964.0681   $964.06   $964.10   $964.10