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	$46.44	8.642%	$50.4533	$50.45	$50.45	$50.50
Purchase #2	$29.57	13.111%	$33.4469	$33.45	$33.45	$33.40
Purchase #3	$119.46	6.575%	$127.3145	$127.31	$127.30	$127.30
Purchase #4	$103.31	4.355%	$107.8092	$107.81	$107.80	$107.80
Purchase #5	$70.45	5.688%	$74.4572	$74.46	$74.45	$74.50
Purchase #6	$148.35	4.219%	$154.6089	$154.61	$154.60	$154.60
Purchase #7	$212.54	7.166%	$227.7706	$227.77	$227.75	$227.80
7 purchase totals =	$730.12		$775.8606	$775.86	$775.80	$775.90