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	$180.91	9.591%	$198.2611	$198.26	$198.25	$198.30
Purchase #2	$207.46	3.329%	$214.3663	$214.37	$214.35	$214.40
Purchase #3	$53.55	7.846%	$57.7515	$57.75	$57.75	$57.80
Purchase #4	$244.45	4.438%	$255.2987	$255.30	$255.30	$255.30
Purchase #5	$37.55	5.816%	$39.7339	$39.73	$39.75	$39.70
Purchase #6	$173.46	10.152%	$191.0697	$191.07	$191.05	$191.10
Purchase #7	$108.85	3.314%	$112.4573	$112.46	$112.45	$112.50
7 purchase totals =	$1,006.23		$1,068.9385	$1,068.94	$1,068.90	$1,069.10