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	$141.31	12.206%	$158.5583	$158.56	$158.55	$158.60
Purchase #2	$61.43	7.178%	$65.8394	$65.84	$65.85	$65.80
Purchase #3	$184.42	4.602%	$192.907	$192.91	$192.90	$192.90
Purchase #4	$96.73	11.756%	$108.1016	$108.10	$108.10	$108.10
Purchase #5	$47.61	13.102%	$53.8479	$53.85	$53.85	$53.80
Purchase #6	$226.33	11.308%	$251.9234	$251.92	$251.90	$251.90
Purchase #7	$51.33	5.128%	$53.9622	$53.96	$53.95	$54.00
7 purchase totals =	$809.16		$885.1398	$885.14	$885.10	$885.10