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	$202.86	13.443%	$230.1305	$230.13	$230.15	$230.10
Purchase #2	$204.44	11.670%	$228.2981	$228.30	$228.30	$228.30
Purchase #3	$14.47	3.661%	$14.9997	$15.00	$15.00	$15.00
Purchase #4	$49.25	7.823%	$53.1028	$53.10	$53.10	$53.10
Purchase #5	$187.64	4.729%	$196.5135	$196.51	$196.50	$196.50
Purchase #6	$94.32	4.447%	$98.5144	$98.51	$98.50	$98.50
Purchase #7	$207.31	7.682%	$223.2356	$223.24	$223.25	$223.20
7 purchase totals =	$960.29		$1,044.7946	$1,044.79	$1,044.80	$1,044.70