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	$176.38	5.129%	$185.4265	$185.43	$185.45	$185.40
Purchase #2	$10.34	12.240%	$11.6056	$11.61	$11.60	$11.60
Purchase #3	$35.77	5.261%	$37.6519	$37.65	$37.65	$37.70
Purchase #4	$107.30	3.536%	$111.0941	$111.09	$111.10	$111.10
Purchase #5	$15.73	7.403%	$16.8945	$16.89	$16.90	$16.90
Purchase #6	$197.70	6.456%	$210.4635	$210.46	$210.45	$210.50
Purchase #7	$57.62	3.613%	$59.7018	$59.70	$59.70	$59.70
7 purchase totals =	$600.84		$632.8379	$632.83	$632.85	$632.90