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 $208.35   11.702%   $232.7311   $232.73   $232.75   $232.70  
  Purchase #2 $222.89   11.329%   $248.1412   $248.14   $248.15   $248.10  
  Purchase #3 $236.29   4.645%   $247.2657   $247.27   $247.25   $247.30  
  Purchase #4 $48.48   10.458%   $53.55   $53.55   $53.55   $53.60  
  Purchase #5 $231.48   8.858%   $251.9845   $251.98   $252.00   $252.00  
  Purchase #6 $249.59   10.294%   $275.2828   $275.28   $275.30   $275.30  
  Purchase #7 $105.68   9.741%   $115.9743   $115.97   $115.95   $116.00  
  7 purchase totals = $1,302.76       $1,424.9296   $1,424.92   $1,424.95   $1,425.00