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	$26.41	12.147%	$29.618	$29.62	$29.60	$29.60
Purchase #2	$165.60	6.636%	$176.5892	$176.59	$176.60	$176.60
Purchase #3	$235.25	13.481%	$266.9641	$266.96	$266.95	$267.00
Purchase #4	$49.90	11.616%	$55.6964	$55.70	$55.70	$55.70
Purchase #5	$173.61	13.311%	$196.7192	$196.72	$196.70	$196.70
Purchase #6	$137.98	7.786%	$148.7231	$148.72	$148.70	$148.70
Purchase #7	$175.52	6.595%	$187.0955	$187.10	$187.10	$187.10
7 purchase totals =	$964.27		$1,061.4055	$1,061.41	$1,061.35	$1,061.40