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	$83.36	5.108%	$87.618	$87.62	$87.60	$87.60
Purchase #2	$49.39	10.498%	$54.575	$54.58	$54.60	$54.60
Purchase #3	$108.38	6.139%	$115.0334	$115.03	$115.05	$115.00
Purchase #4	$38.65	4.688%	$40.4619	$40.46	$40.45	$40.50
Purchase #5	$99.31	4.178%	$103.4592	$103.46	$103.45	$103.50
Purchase #6	$126.41	6.235%	$134.2917	$134.29	$134.30	$134.30
Purchase #7	$55.57	13.545%	$63.097	$63.10	$63.10	$63.10
7 purchase totals =	$561.07		$598.5362	$598.54	$598.55	$598.60