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	$239.60	10.429%	$264.5879	$264.59	$264.60	$264.60
Purchase #2	$191.67	9.631%	$210.1297	$210.13	$210.15	$210.10
Purchase #3	$107.97	3.587%	$111.8429	$111.84	$111.85	$111.80
Purchase #4	$197.65	4.177%	$205.9058	$205.91	$205.90	$205.90
Purchase #5	$88.27	13.626%	$100.2977	$100.30	$100.30	$100.30
Purchase #6	$138.61	8.719%	$150.6954	$150.70	$150.70	$150.70
Purchase #7	$223.92	12.243%	$251.3345	$251.33	$251.35	$251.30
7 purchase totals =	$1,187.69		$1,294.7939	$1,294.80	$1,294.85	$1,294.70