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	$74.37	10.806%	$82.4064	$82.41	$82.40	$82.40
Purchase #2	$242.55	5.470%	$255.8175	$255.82	$255.80	$255.80
Purchase #3	$226.90	3.238%	$234.247	$234.25	$234.25	$234.20
Purchase #4	$132.32	10.166%	$145.7717	$145.77	$145.75	$145.80
Purchase #5	$181.78	9.241%	$198.5783	$198.58	$198.60	$198.60
Purchase #6	$244.45	4.464%	$255.3622	$255.36	$255.35	$255.40
Purchase #7	$94.37	5.469%	$99.5311	$99.53	$99.55	$99.50
7 purchase totals =	$1,196.74		$1,271.7142	$1,271.72	$1,271.70	$1,271.70