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	$210.75	4.651%	$220.552	$220.55	$220.55	$220.60
Purchase #2	$202.79	5.797%	$214.5457	$214.55	$214.55	$214.50
Purchase #3	$116.29	4.554%	$121.5858	$121.59	$121.60	$121.60
Purchase #4	$53.84	10.280%	$59.3748	$59.37	$59.35	$59.40
Purchase #5	$148.84	3.589%	$154.1819	$154.18	$154.20	$154.20
Purchase #6	$105.77	5.487%	$111.5736	$111.57	$111.55	$111.60
Purchase #7	$172.43	10.166%	$189.9592	$189.96	$189.95	$190.00
7 purchase totals =	$1,010.71		$1,071.7730	$1,071.77	$1,071.75	$1,071.90