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	$216.97	4.431%	$226.5839	$226.58	$226.60	$226.60
Purchase #2	$146.82	10.347%	$162.0115	$162.01	$162.00	$162.00
Purchase #3	$55.31	11.780%	$61.8255	$61.83	$61.85	$61.80
Purchase #4	$221.70	9.145%	$241.9745	$241.97	$241.95	$242.00
Purchase #5	$131.57	9.693%	$144.3231	$144.32	$144.30	$144.30
Purchase #6	$49.72	11.857%	$55.6153	$55.62	$55.60	$55.60
Purchase #7	$103.52	7.662%	$111.4517	$111.45	$111.45	$111.50
7 purchase totals =	$925.61		$1,003.7855	$1,003.78	$1,003.75	$1,003.80