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	$225.85	12.466%	$254.0045	$254.00	$254.00	$254.00
Purchase #2	$194.80	12.845%	$219.8221	$219.82	$219.80	$219.80
Purchase #3	$82.41	5.464%	$86.9129	$86.91	$86.90	$86.90
Purchase #4	$143.66	7.643%	$154.6399	$154.64	$154.65	$154.60
Purchase #5	$243.66	6.141%	$258.6232	$258.62	$258.60	$258.60
Purchase #6	$33.92	10.631%	$37.526	$37.53	$37.55	$37.50
Purchase #7	$127.91	7.470%	$137.4649	$137.46	$137.45	$137.50
7 purchase totals =	$1,052.21		$1,148.9935	$1,148.98	$1,148.95	$1,148.90