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	$111.25	5.340%	$117.1908	$117.19	$117.20	$117.20
Purchase #2	$69.80	3.706%	$72.3868	$72.39	$72.40	$72.40
Purchase #3	$227.63	5.513%	$240.1792	$240.18	$240.20	$240.20
Purchase #4	$48.42	13.520%	$54.9664	$54.97	$54.95	$55.00
Purchase #5	$160.98	8.161%	$174.1176	$174.12	$174.10	$174.10
Purchase #6	$122.92	3.453%	$127.1644	$127.16	$127.15	$127.20
Purchase #7	$105.82	5.462%	$111.5999	$111.60	$111.60	$111.60
7 purchase totals =	$846.82		$897.6051	$897.61	$897.60	$897.70