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 $58.95   7.715%   $63.498   $63.50   $63.50   $63.50  
  Purchase #2 $146.61   3.539%   $151.7985   $151.80   $151.80   $151.80  
  Purchase #3 $250.30   12.819%   $282.386   $282.39   $282.40   $282.40  
  Purchase #4 $5.90   5.739%   $6.2386   $6.24   $6.25   $6.20  
  Purchase #5 $139.36   3.357%   $144.0383   $144.04   $144.05   $144.00  
  Purchase #6 $180.98   9.441%   $198.0663   $198.07   $198.05   $198.10  
  Purchase #7 $235.42   6.612%   $250.986   $250.99   $251.00   $251.00  
  7 purchase totals = $1,017.52       $1,097.0117   $1,097.03   $1,097.05   $1,097.00