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	$137.53	4.763%	$144.0806	$144.08	$144.10	$144.10
Purchase #2	$165.85	3.711%	$172.0047	$172.00	$172.00	$172.00
Purchase #3	$165.45	6.710%	$176.5517	$176.55	$176.55	$176.60
Purchase #4	$26.49	9.493%	$29.0047	$29.00	$29.00	$29.00
Purchase #5	$93.43	12.754%	$105.3461	$105.35	$105.35	$105.30
Purchase #6	$107.49	12.112%	$120.5092	$120.51	$120.50	$120.50
Purchase #7	$105.39	12.334%	$118.3888	$118.39	$118.40	$118.40
7 purchase totals =	$801.63		$865.8858	$865.88	$865.90	$865.90