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	$238.73	7.275%	$256.0976	$256.10	$256.10	$256.10
Purchase #2	$204.60	12.832%	$230.8543	$230.85	$230.85	$230.90
Purchase #3	$202.72	4.519%	$211.8809	$211.88	$211.90	$211.90
Purchase #4	$209.42	6.103%	$222.2009	$222.20	$222.20	$222.20
Purchase #5	$119.97	6.188%	$127.3937	$127.39	$127.40	$127.40
Purchase #6	$54.52	4.252%	$56.8382	$56.84	$56.85	$56.80
Purchase #7	$185.57	6.137%	$196.9584	$196.96	$196.95	$197.00
7 purchase totals =	$1,215.53		$1,302.2240	$1,302.22	$1,302.25	$1,302.30