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	$111.93	5.563%	$118.1567	$118.16	$118.15	$118.20
Purchase #2	$29.63	3.229%	$30.5868	$30.59	$30.60	$30.60
Purchase #3	$81.30	11.338%	$90.5178	$90.52	$90.50	$90.50
Purchase #4	$131.90	12.707%	$148.6605	$148.66	$148.65	$148.70
Purchase #5	$193.77	3.104%	$199.7846	$199.78	$199.80	$199.80
Purchase #6	$135.68	4.600%	$141.9213	$141.92	$141.90	$141.90
Purchase #7	$211.84	12.632%	$238.5996	$238.60	$238.60	$238.60
7 purchase totals =	$896.05		$968.2273	$968.23	$968.20	$968.30