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	$248.51	3.139%	$256.3107	$256.31	$256.30	$256.30
Purchase #2	$37.52	5.159%	$39.4557	$39.46	$39.45	$39.50
Purchase #3	$187.98	12.194%	$210.9023	$210.90	$210.90	$210.90
Purchase #4	$39.84	9.817%	$43.7511	$43.75	$43.75	$43.80
Purchase #5	$238.78	11.595%	$266.4665	$266.47	$266.45	$266.50
Purchase #6	$216.81	4.425%	$226.4038	$226.40	$226.40	$226.40
Purchase #7	$101.37	9.523%	$111.0235	$111.02	$111.00	$111.00
7 purchase totals =	$1,070.81		$1,154.3136	$1,154.31	$1,154.25	$1,154.40