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	$235.89	8.621%	$256.2261	$256.23	$256.25	$256.20
Purchase #2	$207.37	13.532%	$235.4313	$235.43	$235.45	$235.40
Purchase #3	$41.84	3.501%	$43.3048	$43.30	$43.30	$43.30
Purchase #4	$76.43	3.145%	$78.8337	$78.83	$78.85	$78.80
Purchase #5	$175.25	13.191%	$198.3672	$198.37	$198.35	$198.40
Purchase #6	$83.53	4.595%	$87.3682	$87.37	$87.35	$87.40
Purchase #7	$230.84	5.810%	$244.2518	$244.25	$244.25	$244.30
7 purchase totals =	$1,051.15		$1,143.7831	$1,143.78	$1,143.80	$1,143.80