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	$151.43	9.107%	$165.2207	$165.22	$165.20	$165.20
Purchase #2	$171.60	11.256%	$190.9153	$190.92	$190.90	$190.90
Purchase #3	$15.69	4.784%	$16.4406	$16.44	$16.45	$16.40
Purchase #4	$73.84	13.133%	$83.5374	$83.54	$83.55	$83.50
Purchase #5	$123.64	10.732%	$136.909	$136.91	$136.90	$136.90
Purchase #6	$125.32	5.599%	$132.3367	$132.34	$132.35	$132.30
Purchase #7	$154.90	3.208%	$159.8692	$159.87	$159.85	$159.90
7 purchase totals =	$816.42		$885.2289	$885.24	$885.20	$885.10