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	$189.97	11.380%	$211.5886	$211.59	$211.60	$211.60
Purchase #2	$111.49	3.754%	$115.6753	$115.68	$115.70	$115.70
Purchase #3	$98.49	7.518%	$105.8945	$105.89	$105.90	$105.90
Purchase #4	$120.90	13.177%	$136.831	$136.83	$136.85	$136.80
Purchase #5	$195.99	4.794%	$205.3858	$205.39	$205.40	$205.40
Purchase #6	$101.83	6.327%	$108.2728	$108.27	$108.25	$108.30
Purchase #7	$125.85	5.797%	$133.1455	$133.15	$133.15	$133.10
7 purchase totals =	$944.52		$1,016.7935	$1,016.80	$1,016.85	$1,016.80