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	$189.96	13.394%	$215.4032	$215.40	$215.40	$215.40
Purchase #2	$223.62	4.406%	$233.4727	$233.47	$233.45	$233.50
Purchase #3	$45.49	4.825%	$47.6849	$47.68	$47.70	$47.70
Purchase #4	$231.63	4.822%	$242.7992	$242.80	$242.80	$242.80
Purchase #5	$161.35	3.152%	$166.4358	$166.44	$166.45	$166.40
Purchase #6	$145.34	4.255%	$151.5242	$151.52	$151.50	$151.50
Purchase #7	$109.88	7.667%	$118.3045	$118.30	$118.30	$118.30
7 purchase totals =	$1,107.27		$1,175.6245	$1,175.61	$1,175.60	$1,175.60