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 $44.69   3.486%   $46.2479   $46.25   $46.25   $46.20  
  Purchase #2 $173.70   6.110%   $184.3131   $184.31   $184.30   $184.30  
  Purchase #3 $159.30   10.140%   $175.453   $175.45   $175.45   $175.50  
  Purchase #4 $224.95   4.569%   $235.228   $235.23   $235.25   $235.20  
  Purchase #5 $124.82   7.792%   $134.546   $134.55   $134.55   $134.50  
  Purchase #6 $235.98   11.444%   $262.9856   $262.99   $263.00   $263.00  
  Purchase #7 $127.28   9.552%   $139.4378   $139.44   $139.45   $139.40  
  7 purchase totals = $1,090.72       $1,178.2114   $1,178.22   $1,178.25   $1,178.10