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	$240.90	4.399%	$251.4972	$251.50	$251.50	$251.50
Purchase #2	$146.46	3.295%	$151.2859	$151.29	$151.30	$151.30
Purchase #3	$144.94	13.123%	$163.9605	$163.96	$163.95	$164.00
Purchase #4	$40.86	7.475%	$43.9143	$43.91	$43.90	$43.90
Purchase #5	$135.52	11.862%	$151.5954	$151.60	$151.60	$151.60
Purchase #6	$102.56	11.763%	$114.6241	$114.62	$114.60	$114.60
Purchase #7	$158.55	6.280%	$168.5069	$168.51	$168.50	$168.50
7 purchase totals =	$969.79		$1,045.3843	$1,045.39	$1,045.35	$1,045.40