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	$48.42	6.446%	$51.5412	$51.54	$51.55	$51.50
Purchase #2	$89.69	12.707%	$101.0869	$101.09	$101.10	$101.10
Purchase #3	$198.25	11.388%	$220.8267	$220.83	$220.85	$220.80
Purchase #4	$177.90	3.201%	$183.5946	$183.59	$183.60	$183.60
Purchase #5	$232.86	4.382%	$243.0639	$243.06	$243.05	$243.10
Purchase #6	$158.77	9.429%	$173.7404	$173.74	$173.75	$173.70
Purchase #7	$109.63	12.443%	$123.2713	$123.27	$123.25	$123.30
7 purchase totals =	$1,015.52		$1,097.1250	$1,097.12	$1,097.15	$1,097.10