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 $41.94   13.526%   $47.6128   $47.61   $47.60   $47.60  
  Purchase #2 $207.57   9.783%   $227.8766   $227.88   $227.90   $227.90  
  Purchase #3 $233.76   6.808%   $249.6744   $249.67   $249.65   $249.70  
  Purchase #4 $30.41   12.591%   $34.2389   $34.24   $34.25   $34.20  
  Purchase #5 $95.41   11.127%   $106.0263   $106.03   $106.05   $106.00  
  Purchase #6 $181.69   4.741%   $190.3039   $190.30   $190.30   $190.30  
  Purchase #7 $196.72   10.721%   $217.8104   $217.81   $217.80   $217.80  
  7 purchase totals = $987.50       $1,073.5433   $1,073.54   $1,073.55   $1,073.50