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	$107.95	8.477%	$117.1009	$117.10	$117.10	$117.10
Purchase #2	$73.44	7.286%	$78.7908	$78.79	$78.80	$78.80
Purchase #3	$199.88	3.109%	$206.0943	$206.09	$206.10	$206.10
Purchase #4	$225.92	11.453%	$251.7946	$251.79	$251.80	$251.80
Purchase #5	$104.60	6.793%	$111.7055	$111.71	$111.70	$111.70
Purchase #6	$120.83	11.332%	$134.5225	$134.52	$134.50	$134.50
Purchase #7	$241.69	5.303%	$254.5068	$254.51	$254.50	$254.50
7 purchase totals =	$1,074.31		$1,154.5154	$1,154.51	$1,154.50	$1,154.50