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 $114.27   9.751%   $125.4125   $125.41   $125.40   $125.40  
  Purchase #2 $236.54   6.676%   $252.3314   $252.33   $252.35   $252.30  
  Purchase #3 $147.61   3.552%   $152.8531   $152.85   $152.85   $152.90  
  Purchase #4 $178.38   3.243%   $184.1649   $184.16   $184.15   $184.20  
  Purchase #5 $196.61   8.836%   $213.9825   $213.98   $214.00   $214.00  
  Purchase #6 $68.86   8.123%   $74.4535   $74.45   $74.45   $74.50  
  Purchase #7 $9.79   11.488%   $10.9147   $10.91   $10.90   $10.90  
  7 purchase totals = $952.06       $1,014.1126   $1,014.09   $1,014.10   $1,014.20