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	$137.69	11.570%	$153.6207	$153.62	$153.60	$153.60
Purchase #2	$224.49	8.179%	$242.851	$242.85	$242.85	$242.90
Purchase #3	$103.83	7.406%	$111.5196	$111.52	$111.50	$111.50
Purchase #4	$144.58	3.381%	$149.4682	$149.47	$149.45	$149.50
Purchase #5	$239.60	3.162%	$247.1762	$247.18	$247.20	$247.20
Purchase #6	$101.88	12.371%	$114.4836	$114.48	$114.50	$114.50
Purchase #7	$41.86	11.465%	$46.6592	$46.66	$46.65	$46.70
7 purchase totals =	$993.93		$1,065.7785	$1,065.78	$1,065.75	$1,065.90