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	$56.27	9.444%	$61.5841	$61.58	$61.60	$61.60
Purchase #2	$51.52	5.384%	$54.2938	$54.29	$54.30	$54.30
Purchase #3	$58.58	13.552%	$66.5188	$66.52	$66.50	$66.50
Purchase #4	$115.70	13.408%	$131.2131	$131.21	$131.20	$131.20
Purchase #5	$40.76	10.611%	$45.085	$45.09	$45.10	$45.10
Purchase #6	$177.88	13.424%	$201.7586	$201.76	$201.75	$201.80
Purchase #7	$44.59	5.682%	$47.1236	$47.12	$47.10	$47.10
7 purchase totals =	$545.30		$607.5770	$607.57	$607.55	$607.60