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	$164.88	12.301%	$185.1619	$185.16	$185.15	$185.20
Purchase #2	$101.98	9.760%	$111.9332	$111.93	$111.95	$111.90
Purchase #3	$214.73	8.752%	$233.5232	$233.52	$233.50	$233.50
Purchase #4	$229.69	6.545%	$244.7232	$244.72	$244.70	$244.70
Purchase #5	$98.99	12.755%	$111.6162	$111.62	$111.60	$111.60
Purchase #6	$126.63	4.603%	$132.4588	$132.46	$132.45	$132.50
Purchase #7	$212.57	13.259%	$240.7547	$240.75	$240.75	$240.80
7 purchase totals =	$1,149.47		$1,260.1712	$1,260.16	$1,260.10	$1,260.20