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	$112.33	5.326%	$118.3127	$118.31	$118.30	$118.30
Purchase #2	$165.75	3.201%	$171.0557	$171.06	$171.05	$171.10
Purchase #3	$193.78	10.716%	$214.5455	$214.55	$214.55	$214.50
Purchase #4	$205.39	3.833%	$213.2626	$213.26	$213.25	$213.30
Purchase #5	$107.77	8.382%	$116.8033	$116.80	$116.80	$116.80
Purchase #6	$79.68	12.777%	$89.8607	$89.86	$89.85	$89.90
Purchase #7	$34.60	10.664%	$38.2897	$38.29	$38.30	$38.30
7 purchase totals =	$899.30		$962.1302	$962.13	$962.10	$962.20