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	$143.49	8.636%	$155.8818	$155.88	$155.90	$155.90
Purchase #2	$138.42	9.429%	$151.4716	$151.47	$151.45	$151.50
Purchase #3	$89.47	7.864%	$96.5059	$96.51	$96.50	$96.50
Purchase #4	$233.46	6.731%	$249.1742	$249.17	$249.15	$249.20
Purchase #5	$206.88	9.160%	$225.8302	$225.83	$225.85	$225.80
Purchase #6	$64.45	3.126%	$66.4647	$66.46	$66.45	$66.50
Purchase #7	$109.94	12.514%	$123.6979	$123.70	$123.70	$123.70
7 purchase totals =	$986.11		$1,069.0263	$1,069.02	$1,069.00	$1,069.10