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	$145.41	7.575%	$156.4248	$156.42	$156.40	$156.40
Purchase #2	$117.40	7.728%	$126.4727	$126.47	$126.45	$126.50
Purchase #3	$171.30	5.190%	$180.1905	$180.19	$180.20	$180.20
Purchase #4	$206.47	6.513%	$219.9174	$219.92	$219.90	$219.90
Purchase #5	$103.40	8.105%	$111.7806	$111.78	$111.80	$111.80
Purchase #6	$53.39	5.706%	$56.4364	$56.44	$56.45	$56.40
Purchase #7	$39.90	11.184%	$44.3624	$44.36	$44.35	$44.40
7 purchase totals =	$837.27		$895.5848	$895.58	$895.55	$895.60