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	$197.89	3.341%	$204.5015	$204.50	$204.50	$204.50
Purchase #2	$100.89	11.835%	$112.8303	$112.83	$112.85	$112.80
Purchase #3	$92.52	13.874%	$105.3562	$105.36	$105.35	$105.40
Purchase #4	$173.66	9.201%	$189.6385	$189.64	$189.65	$189.60
Purchase #5	$180.74	13.838%	$205.7508	$205.75	$205.75	$205.80
Purchase #6	$204.86	9.264%	$223.8382	$223.84	$223.85	$223.80
Purchase #7	$101.76	6.521%	$108.3958	$108.40	$108.40	$108.40
7 purchase totals =	$1,052.32		$1,150.3113	$1,150.32	$1,150.35	$1,150.30