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	$42.66	6.747%	$45.5383	$45.54	$45.55	$45.50
Purchase #2	$226.29	13.241%	$256.2531	$256.25	$256.25	$256.30
Purchase #3	$250.51	8.613%	$272.0864	$272.09	$272.10	$272.10
Purchase #4	$174.26	9.647%	$191.0709	$191.07	$191.05	$191.10
Purchase #5	$114.39	4.283%	$119.2893	$119.29	$119.30	$119.30
Purchase #6	$100.70	10.404%	$111.1768	$111.18	$111.20	$111.20
Purchase #7	$242.81	4.423%	$253.5495	$253.55	$253.55	$253.50
7 purchase totals =	$1,151.62		$1,248.9643	$1,248.97	$1,249.00	$1,249.00