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 $44.45   4.116%   $46.2796   $46.28   $46.30   $46.30  
  Purchase #2 $185.93   8.637%   $201.9888   $201.99   $202.00   $202.00  
  Purchase #3 $222.37   8.546%   $241.3737   $241.37   $241.35   $241.40  
  Purchase #4 $19.53   9.865%   $21.4566   $21.46   $21.45   $21.50  
  Purchase #5 $115.43   4.166%   $120.2388   $120.24   $120.25   $120.20  
  Purchase #6 $243.69   12.518%   $274.1951   $274.20   $274.20   $274.20  
  Purchase #7 $130.28   6.864%   $139.2224   $139.22   $139.20   $139.20  
  7 purchase totals = $961.68       $1,044.7550   $1,044.76   $1,044.75   $1,044.80