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	$146.63	7.301%	$157.3355	$157.34	$157.35	$157.30
Purchase #2	$241.28	3.786%	$250.4149	$250.41	$250.40	$250.40
Purchase #3	$213.69	13.116%	$241.7176	$241.72	$241.70	$241.70
Purchase #4	$51.45	6.131%	$54.6044	$54.60	$54.60	$54.60
Purchase #5	$102.90	8.540%	$111.6877	$111.69	$111.70	$111.70
Purchase #6	$153.31	8.757%	$166.7354	$166.74	$166.75	$166.70
Purchase #7	$101.97	3.412%	$105.4492	$105.45	$105.45	$105.40
7 purchase totals =	$1,011.23		$1,087.9447	$1,087.95	$1,087.95	$1,087.80