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 $192.75   5.440%   $203.2356   $203.24   $203.25   $203.20  
  Purchase #2 $114.69   3.484%   $118.6858   $118.69   $118.70   $118.70  
  Purchase #3 $214.51   7.525%   $230.6519   $230.65   $230.65   $230.70  
  Purchase #4 $177.60   13.686%   $201.9063   $201.91   $201.90   $201.90  
  Purchase #5 $47.60   5.186%   $50.0685   $50.07   $50.05   $50.10  
  Purchase #6 $128.67   3.698%   $133.4282   $133.43   $133.45   $133.40  
  Purchase #7 $98.26   8.445%   $106.5581   $106.56   $106.55   $106.60  
  7 purchase totals = $974.08       $1,044.5344   $1,044.55   $1,044.55   $1,044.60