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	$166.81	13.438%	$189.2259	$189.23	$189.25	$189.20
Purchase #2	$81.75	9.466%	$89.4885	$89.49	$89.50	$89.50
Purchase #3	$102.92	12.867%	$116.1627	$116.16	$116.15	$116.20
Purchase #4	$231.86	5.361%	$244.29	$244.29	$244.30	$244.30
Purchase #5	$230.95	13.693%	$262.574	$262.57	$262.55	$262.60
Purchase #6	$52.36	13.358%	$59.3542	$59.35	$59.35	$59.40
Purchase #7	$234.93	4.403%	$245.274	$245.27	$245.25	$245.30
7 purchase totals =	$1,101.58		$1,206.3693	$1,206.36	$1,206.35	$1,206.50