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	$224.78	12.513%	$252.9067	$252.91	$252.90	$252.90
Purchase #2	$146.89	3.105%	$151.4509	$151.45	$151.45	$151.50
Purchase #3	$100.95	4.350%	$105.3413	$105.34	$105.35	$105.30
Purchase #4	$250.30	10.816%	$277.3724	$277.37	$277.35	$277.40
Purchase #5	$224.37	9.160%	$244.9223	$244.92	$244.90	$244.90
Purchase #6	$59.34	4.506%	$62.0139	$62.01	$62.00	$62.00
Purchase #7	$130.42	10.447%	$144.045	$144.05	$144.05	$144.00
7 purchase totals =	$1,137.05		$1,238.0525	$1,238.05	$1,238.00	$1,238.00