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	$137.35	13.550%	$155.9609	$155.96	$155.95	$156.00
Purchase #2	$11.48	3.410%	$11.8715	$11.87	$11.85	$11.90
Purchase #3	$166.62	11.717%	$186.1429	$186.14	$186.15	$186.10
Purchase #4	$113.91	8.152%	$123.1959	$123.20	$123.20	$123.20
Purchase #5	$108.72	5.650%	$114.8627	$114.86	$114.85	$114.90
Purchase #6	$107.85	3.704%	$111.8448	$111.84	$111.85	$111.80
Purchase #7	$38.74	4.534%	$40.4965	$40.50	$40.50	$40.50
7 purchase totals =	$684.67		$744.3752	$744.37	$744.35	$744.40