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	$199.69	13.429%	$226.5064	$226.51	$226.50	$226.50
Purchase #2	$89.50	8.257%	$96.89	$96.89	$96.90	$96.90
Purchase #3	$158.81	4.847%	$166.5075	$166.51	$166.50	$166.50
Purchase #4	$178.88	12.176%	$200.6604	$200.66	$200.65	$200.70
Purchase #5	$80.88	12.616%	$91.0838	$91.08	$91.10	$91.10
Purchase #6	$182.37	13.628%	$207.2234	$207.22	$207.20	$207.20
Purchase #7	$11.82	3.358%	$12.2169	$12.22	$12.20	$12.20
7 purchase totals =	$901.95		$1,001.0884	$1,001.09	$1,001.05	$1,001.10