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	$114.40	4.449%	$119.4897	$119.49	$119.50	$119.50
Purchase #2	$130.68	10.705%	$144.6693	$144.67	$144.65	$144.70
Purchase #3	$191.64	11.363%	$213.4161	$213.42	$213.40	$213.40
Purchase #4	$43.84	6.766%	$46.8062	$46.81	$46.80	$46.80
Purchase #5	$107.92	3.574%	$111.7771	$111.78	$111.80	$111.80
Purchase #6	$99.47	8.236%	$107.6623	$107.66	$107.65	$107.70
Purchase #7	$174.85	12.306%	$196.367	$196.37	$196.35	$196.40
7 purchase totals =	$862.80		$940.1877	$940.20	$940.15	$940.30