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	$214.76	11.824%	$240.1532	$240.15	$240.15	$240.20
Purchase #2	$71.92	13.411%	$81.5652	$81.57	$81.55	$81.60
Purchase #3	$56.52	10.255%	$62.3161	$62.32	$62.30	$62.30
Purchase #4	$216.27	9.605%	$237.0427	$237.04	$237.05	$237.00
Purchase #5	$145.91	6.801%	$155.8333	$155.83	$155.85	$155.80
Purchase #6	$244.49	4.605%	$255.7488	$255.75	$255.75	$255.70
Purchase #7	$117.51	8.751%	$127.7933	$127.79	$127.80	$127.80
7 purchase totals =	$1,067.38		$1,160.4526	$1,160.45	$1,160.45	$1,160.40