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	$40.98	6.466%	$43.6298	$43.63	$43.65	$43.60
Purchase #2	$238.25	7.465%	$256.0354	$256.04	$256.05	$256.00
Purchase #3	$162.71	10.572%	$179.9117	$179.91	$179.90	$179.90
Purchase #4	$128.71	4.343%	$134.2999	$134.30	$134.30	$134.30
Purchase #5	$244.81	4.361%	$255.4862	$255.49	$255.50	$255.50
Purchase #6	$239.86	4.867%	$251.534	$251.53	$251.55	$251.50
Purchase #7	$137.32	5.418%	$144.76	$144.76	$144.75	$144.80
7 purchase totals =	$1,192.64		$1,265.6570	$1,265.66	$1,265.70	$1,265.60