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	$181.36	10.636%	$200.6494	$200.65	$200.65	$200.60
Purchase #2	$191.53	12.519%	$215.5076	$215.51	$215.50	$215.50
Purchase #3	$198.32	8.795%	$215.7622	$215.76	$215.75	$215.80
Purchase #4	$192.42	13.416%	$218.2351	$218.24	$218.25	$218.20
Purchase #5	$111.78	13.619%	$127.0033	$127.00	$127.00	$127.00
Purchase #6	$239.95	10.770%	$265.7926	$265.79	$265.80	$265.80
Purchase #7	$184.82	11.103%	$205.3406	$205.34	$205.35	$205.30
7 purchase totals =	$1,300.18		$1,448.2908	$1,448.29	$1,448.30	$1,448.20