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	$138.61	10.154%	$152.6845	$152.68	$152.70	$152.70
Purchase #2	$60.99	10.651%	$67.486	$67.49	$67.50	$67.50
Purchase #3	$45.79	5.387%	$48.2567	$48.26	$48.25	$48.30
Purchase #4	$87.35	13.589%	$99.22	$99.22	$99.20	$99.20
Purchase #5	$123.92	7.396%	$133.0851	$133.09	$133.10	$133.10
Purchase #6	$67.30	6.404%	$71.6099	$71.61	$71.60	$71.60
Purchase #7	$195.65	6.554%	$208.4729	$208.47	$208.45	$208.50
7 purchase totals =	$719.61		$780.8151	$780.82	$780.80	$780.90