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	$248.84	5.489%	$262.4988	$262.50	$262.50	$262.50
Purchase #2	$26.34	12.253%	$29.5674	$29.57	$29.55	$29.60
Purchase #3	$190.29	13.441%	$215.8669	$215.87	$215.85	$215.90
Purchase #4	$98.71	5.230%	$103.8725	$103.87	$103.85	$103.90
Purchase #5	$35.81	12.558%	$40.307	$40.31	$40.30	$40.30
Purchase #6	$248.60	12.469%	$279.5979	$279.60	$279.60	$279.60
Purchase #7	$219.29	9.193%	$239.4493	$239.45	$239.45	$239.40
7 purchase totals =	$1,067.88		$1,171.1598	$1,171.17	$1,171.10	$1,171.20