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	$199.79	3.758%	$207.2981	$207.30	$207.30	$207.30
Purchase #2	$45.78	3.569%	$47.4139	$47.41	$47.40	$47.40
Purchase #3	$102.92	8.747%	$111.9224	$111.92	$111.90	$111.90
Purchase #4	$161.90	13.198%	$183.2676	$183.27	$183.25	$183.30
Purchase #5	$169.52	9.595%	$185.7854	$185.79	$185.80	$185.80
Purchase #6	$249.50	13.276%	$282.6236	$282.62	$282.60	$282.60
Purchase #7	$154.44	11.496%	$172.1944	$172.19	$172.20	$172.20
7 purchase totals =	$1,083.85		$1,190.5054	$1,190.50	$1,190.45	$1,190.50