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	$204.57	5.343%	$215.5002	$215.50	$215.50	$215.50
Purchase #2	$35.31	6.422%	$37.5776	$37.58	$37.60	$37.60
Purchase #3	$62.32	5.228%	$65.5781	$65.58	$65.60	$65.60
Purchase #4	$53.94	7.423%	$57.944	$57.94	$57.95	$57.90
Purchase #5	$124.51	3.210%	$128.5068	$128.51	$128.50	$128.50
Purchase #6	$159.67	10.400%	$176.2757	$176.28	$176.30	$176.30
Purchase #7	$52.44	8.147%	$56.7123	$56.71	$56.70	$56.70
7 purchase totals =	$692.76		$738.0947	$738.10	$738.15	$738.10