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	$84.25	9.653%	$92.3827	$92.38	$92.40	$92.40
Purchase #2	$105.64	5.256%	$111.1924	$111.19	$111.20	$111.20
Purchase #3	$48.45	5.384%	$51.0585	$51.06	$51.05	$51.10
Purchase #4	$222.45	13.189%	$251.7889	$251.79	$251.80	$251.80
Purchase #5	$52.46	13.183%	$59.3758	$59.38	$59.40	$59.40
Purchase #6	$110.39	5.228%	$116.1612	$116.16	$116.15	$116.20
Purchase #7	$107.43	13.840%	$122.2983	$122.30	$122.30	$122.30
7 purchase totals =	$731.07		$804.2578	$804.26	$804.30	$804.40