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	$195.49	11.460%	$217.8932	$217.89	$217.90	$217.90
Purchase #2	$218.95	5.451%	$230.885	$230.89	$230.90	$230.90
Purchase #3	$79.41	4.212%	$82.7547	$82.75	$82.75	$82.80
Purchase #4	$46.49	4.593%	$48.6253	$48.63	$48.65	$48.60
Purchase #5	$46.91	10.490%	$51.8309	$51.83	$51.85	$51.80
Purchase #6	$129.98	12.323%	$145.9974	$146.00	$146.00	$146.00
Purchase #7	$194.89	10.623%	$215.5932	$215.59	$215.60	$215.60
7 purchase totals =	$912.12		$993.5797	$993.58	$993.65	$993.60