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	$153.47	13.779%	$174.6166	$174.62	$174.60	$174.60
Purchase #2	$70.32	11.558%	$78.4476	$78.45	$78.45	$78.40
Purchase #3	$206.77	7.546%	$222.3729	$222.37	$222.35	$222.40
Purchase #4	$115.37	6.365%	$122.7133	$122.71	$122.70	$122.70
Purchase #5	$129.31	4.103%	$134.6156	$134.62	$134.60	$134.60
Purchase #6	$179.46	11.849%	$200.7242	$200.72	$200.70	$200.70
Purchase #7	$122.41	11.267%	$136.2019	$136.20	$136.20	$136.20
7 purchase totals =	$977.11		$1,069.6921	$1,069.69	$1,069.60	$1,069.60