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	$220.35	3.546%	$228.1636	$228.16	$228.15	$228.20
Purchase #2	$41.32	3.711%	$42.8534	$42.85	$42.85	$42.90
Purchase #3	$154.77	6.647%	$165.0576	$165.06	$165.05	$165.10
Purchase #4	$203.71	11.479%	$227.0939	$227.09	$227.10	$227.10
Purchase #5	$237.91	10.528%	$262.9572	$262.96	$262.95	$263.00
Purchase #6	$101.47	10.640%	$112.2664	$112.27	$112.25	$112.30
Purchase #7	$157.39	9.429%	$172.2303	$172.23	$172.25	$172.20
7 purchase totals =	$1,116.92		$1,210.6224	$1,210.62	$1,210.60	$1,210.80