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	$104.55	6.431%	$111.2736	$111.27	$111.25	$111.30
Purchase #2	$183.59	6.587%	$195.6831	$195.68	$195.70	$195.70
Purchase #3	$49.78	6.639%	$53.0849	$53.08	$53.10	$53.10
Purchase #4	$19.92	6.691%	$21.2528	$21.25	$21.25	$21.30
Purchase #5	$225.80	9.195%	$246.5623	$246.56	$246.55	$246.60
Purchase #6	$105.60	6.525%	$112.4904	$112.49	$112.50	$112.50
Purchase #7	$239.33	13.260%	$271.0652	$271.07	$271.05	$271.10
7 purchase totals =	$928.57		$1,011.4123	$1,011.40	$1,011.40	$1,011.60