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	$100.39	11.422%	$111.8565	$111.86	$111.85	$111.90
Purchase #2	$204.47	5.255%	$215.2149	$215.21	$215.20	$215.20
Purchase #3	$243.85	3.366%	$252.058	$252.06	$252.05	$252.10
Purchase #4	$48.39	13.303%	$54.8273	$54.83	$54.85	$54.80
Purchase #5	$150.98	11.656%	$168.5782	$168.58	$168.60	$168.60
Purchase #6	$227.95	6.298%	$242.3063	$242.31	$242.30	$242.30
Purchase #7	$51.66	12.600%	$58.1692	$58.17	$58.15	$58.20
7 purchase totals =	$1,027.69		$1,103.0104	$1,103.02	$1,103.00	$1,103.10