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	$7.32	4.142%	$7.6232	$7.62	$7.60	$7.60
Purchase #2	$158.43	12.239%	$177.8202	$177.82	$177.80	$177.80
Purchase #3	$41.42	5.824%	$43.8323	$43.83	$43.85	$43.80
Purchase #4	$223.85	13.754%	$254.6383	$254.64	$254.65	$254.60
Purchase #5	$156.34	10.436%	$172.6556	$172.66	$172.65	$172.70
Purchase #6	$142.58	5.481%	$150.3948	$150.39	$150.40	$150.40
Purchase #7	$126.31	3.643%	$130.9115	$130.91	$130.90	$130.90
7 purchase totals =	$856.25		$937.8759	$937.87	$937.85	$937.80