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	$176.52	10.217%	$194.555	$194.56	$194.55	$194.60
Purchase #2	$126.89	3.568%	$131.4174	$131.42	$131.40	$131.40
Purchase #3	$82.69	12.253%	$92.822	$92.82	$92.80	$92.80
Purchase #4	$95.53	8.183%	$103.3472	$103.35	$103.35	$103.30
Purchase #5	$196.51	10.722%	$217.5798	$217.58	$217.60	$217.60
Purchase #6	$7.80	3.400%	$8.0652	$8.07	$8.05	$8.10
Purchase #7	$212.52	8.374%	$230.3164	$230.32	$230.30	$230.30
7 purchase totals =	$898.46		$978.1030	$978.12	$978.05	$978.10