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	$118.73	4.341%	$123.8841	$123.88	$123.90	$123.90
Purchase #2	$114.51	8.827%	$124.6178	$124.62	$124.60	$124.60
Purchase #3	$48.48	7.217%	$51.9788	$51.98	$52.00	$52.00
Purchase #4	$245.58	13.352%	$278.3698	$278.37	$278.35	$278.40
Purchase #5	$220.75	5.123%	$232.059	$232.06	$232.05	$232.10
Purchase #6	$160.47	4.164%	$167.152	$167.15	$167.15	$167.20
Purchase #7	$115.63	10.553%	$127.8324	$127.83	$127.85	$127.80
7 purchase totals =	$1,024.15		$1,105.8939	$1,105.89	$1,105.90	$1,106.00