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	$111.27	4.409%	$116.1759	$116.18	$116.20	$116.20
Purchase #2	$222.63	3.518%	$230.4621	$230.46	$230.45	$230.50
Purchase #3	$178.31	10.159%	$196.4245	$196.42	$196.40	$196.40
Purchase #4	$133.45	5.844%	$141.2488	$141.25	$141.25	$141.20
Purchase #5	$203.79	10.646%	$225.4855	$225.49	$225.50	$225.50
Purchase #6	$29.47	10.784%	$32.648	$32.65	$32.65	$32.60
Purchase #7	$215.70	5.846%	$228.3098	$228.31	$228.30	$228.30
7 purchase totals =	$1,094.62		$1,170.7546	$1,170.76	$1,170.75	$1,170.70