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	$106.58	4.639%	$111.5242	$111.52	$111.50	$111.50
Purchase #2	$138.71	4.411%	$144.8285	$144.83	$144.85	$144.80
Purchase #3	$67.89	4.243%	$70.7706	$70.77	$70.75	$70.80
Purchase #4	$177.34	8.255%	$191.9794	$191.98	$192.00	$192.00
Purchase #5	$196.76	13.488%	$223.299	$223.30	$223.30	$223.30
Purchase #6	$62.39	11.565%	$69.6054	$69.61	$69.60	$69.60
Purchase #7	$248.43	4.642%	$259.9621	$259.96	$259.95	$260.00
7 purchase totals =	$998.10		$1,071.9692	$1,071.97	$1,071.95	$1,072.00