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	$118.63	8.453%	$128.6578	$128.66	$128.65	$128.70
Purchase #2	$143.54	10.426%	$158.5055	$158.51	$158.50	$158.50
Purchase #3	$96.37	12.527%	$108.4423	$108.44	$108.45	$108.40
Purchase #4	$35.98	12.834%	$40.5977	$40.60	$40.60	$40.60
Purchase #5	$192.59	9.863%	$211.5852	$211.59	$211.60	$211.60
Purchase #6	$176.98	5.335%	$186.4219	$186.42	$186.40	$186.40
Purchase #7	$194.31	10.768%	$215.2333	$215.23	$215.25	$215.20
7 purchase totals =	$958.40		$1,049.4437	$1,049.45	$1,049.45	$1,049.40