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	$101.50	8.741%	$110.3721	$110.37	$110.35	$110.40
Purchase #2	$184.44	11.267%	$205.2209	$205.22	$205.20	$205.20
Purchase #3	$118.26	4.393%	$123.4552	$123.46	$123.45	$123.50
Purchase #4	$97.54	13.806%	$111.0064	$111.01	$111.00	$111.00
Purchase #5	$61.95	3.356%	$64.029	$64.03	$64.05	$64.00
Purchase #6	$52.93	3.296%	$54.6746	$54.67	$54.65	$54.70
Purchase #7	$113.75	11.782%	$127.152	$127.15	$127.15	$127.20
7 purchase totals =	$730.37		$795.9102	$795.91	$795.85	$796.00