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	$39.36	11.748%	$43.984	$43.98	$44.00	$44.00
Purchase #2	$231.31	10.514%	$255.6299	$255.63	$255.65	$255.60
Purchase #3	$19.52	3.163%	$20.1374	$20.14	$20.15	$20.10
Purchase #4	$165.29	13.308%	$187.2868	$187.29	$187.30	$187.30
Purchase #5	$211.76	10.354%	$233.6856	$233.69	$233.70	$233.70
Purchase #6	$10.94	12.479%	$12.3052	$12.31	$12.30	$12.30
Purchase #7	$142.42	5.436%	$150.162	$150.16	$150.15	$150.20
7 purchase totals =	$820.60		$903.1909	$903.20	$903.25	$903.20