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	$181.79	3.837%	$188.7653	$188.77	$188.75	$188.80
Purchase #2	$128.31	10.388%	$141.6388	$141.64	$141.65	$141.60
Purchase #3	$210.92	8.502%	$228.8524	$228.85	$228.85	$228.90
Purchase #4	$101.31	4.348%	$105.715	$105.72	$105.70	$105.70
Purchase #5	$44.67	4.297%	$46.5895	$46.59	$46.60	$46.60
Purchase #6	$49.43	10.104%	$54.4244	$54.42	$54.40	$54.40
Purchase #7	$244.69	10.783%	$271.0749	$271.07	$271.05	$271.10
7 purchase totals =	$961.12		$1,037.0603	$1,037.06	$1,037.00	$1,037.10