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	$108.43	9.371%	$118.591	$118.59	$118.60	$118.60
Purchase #2	$149.60	5.773%	$158.2364	$158.24	$158.25	$158.20
Purchase #3	$129.69	8.351%	$140.5204	$140.52	$140.50	$140.50
Purchase #4	$123.49	13.212%	$139.8055	$139.81	$139.80	$139.80
Purchase #5	$32.28	12.257%	$36.2366	$36.24	$36.25	$36.20
Purchase #6	$111.62	6.299%	$118.6509	$118.65	$118.65	$118.70
Purchase #7	$129.46	11.437%	$144.2663	$144.27	$144.25	$144.30
7 purchase totals =	$784.57		$856.3071	$856.32	$856.30	$856.30