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	$40.70	6.760%	$43.4513	$43.45	$43.45	$43.50
Purchase #2	$178.30	11.169%	$198.2143	$198.21	$198.20	$198.20
Purchase #3	$214.39	4.243%	$223.4866	$223.49	$223.50	$223.50
Purchase #4	$126.30	4.560%	$132.0593	$132.06	$132.05	$132.10
Purchase #5	$103.85	5.298%	$109.352	$109.35	$109.35	$109.40
Purchase #6	$159.59	8.426%	$173.0371	$173.04	$173.05	$173.00
Purchase #7	$224.82	7.367%	$241.3825	$241.38	$241.40	$241.40
7 purchase totals =	$1,047.95		$1,120.9831	$1,120.98	$1,121.00	$1,121.10