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	$121.36	4.661%	$127.0166	$127.02	$127.00	$127.00
Purchase #2	$112.49	13.536%	$127.7166	$127.72	$127.70	$127.70
Purchase #3	$177.40	4.536%	$185.4469	$185.45	$185.45	$185.40
Purchase #4	$194.62	11.832%	$217.6474	$217.65	$217.65	$217.60
Purchase #5	$124.59	3.184%	$128.5569	$128.56	$128.55	$128.60
Purchase #6	$158.61	13.825%	$180.5378	$180.54	$180.55	$180.50
Purchase #7	$50.39	4.721%	$52.7689	$52.77	$52.75	$52.80
7 purchase totals =	$939.46		$1,019.6911	$1,019.71	$1,019.65	$1,019.60