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	$197.45	8.643%	$214.5156	$214.52	$214.50	$214.50
Purchase #2	$106.30	7.313%	$114.0737	$114.07	$114.05	$114.10
Purchase #3	$134.66	12.513%	$151.51	$151.51	$151.50	$151.50
Purchase #4	$114.66	7.853%	$123.6642	$123.66	$123.65	$123.70
Purchase #5	$237.37	8.303%	$257.0788	$257.08	$257.10	$257.10
Purchase #6	$95.56	3.712%	$99.1072	$99.11	$99.10	$99.10
Purchase #7	$126.84	3.462%	$131.2312	$131.23	$131.25	$131.20
7 purchase totals =	$1,012.84		$1,091.1807	$1,091.18	$1,091.15	$1,091.20