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	$113.76	11.712%	$127.0836	$127.08	$127.10	$127.10
Purchase #2	$235.30	10.738%	$260.5665	$260.57	$260.55	$260.60
Purchase #3	$143.86	6.448%	$153.1361	$153.14	$153.15	$153.10
Purchase #4	$85.39	10.459%	$94.3209	$94.32	$94.30	$94.30
Purchase #5	$165.85	11.256%	$184.5181	$184.52	$184.50	$184.50
Purchase #6	$237.98	10.776%	$263.6247	$263.62	$263.60	$263.60
Purchase #7	$151.64	13.733%	$172.4647	$172.46	$172.45	$172.50
7 purchase totals =	$1,133.78		$1,255.7146	$1,255.71	$1,255.65	$1,255.70