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	$214.42	7.694%	$230.9175	$230.92	$230.90	$230.90
Purchase #2	$59.41	6.178%	$63.0803	$63.08	$63.10	$63.10
Purchase #3	$54.95	12.488%	$61.8122	$61.81	$61.80	$61.80
Purchase #4	$112.33	9.746%	$123.2777	$123.28	$123.30	$123.30
Purchase #5	$242.34	3.344%	$250.4438	$250.44	$250.45	$250.40
Purchase #6	$90.67	10.401%	$100.1006	$100.10	$100.10	$100.10
Purchase #7	$126.52	4.155%	$131.7769	$131.78	$131.80	$131.80
7 purchase totals =	$900.64		$961.4090	$961.41	$961.45	$961.40