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	$107.60	3.781%	$111.6684	$111.67	$111.65	$111.70
Purchase #2	$39.40	7.454%	$42.3369	$42.34	$42.35	$42.30
Purchase #3	$59.59	5.218%	$62.6994	$62.70	$62.70	$62.70
Purchase #4	$95.30	9.265%	$104.1295	$104.13	$104.15	$104.10
Purchase #5	$46.38	8.264%	$50.2128	$50.21	$50.20	$50.20
Purchase #6	$167.98	5.211%	$176.7334	$176.73	$176.75	$176.70
Purchase #7	$129.31	12.324%	$145.2462	$145.25	$145.25	$145.20
7 purchase totals =	$645.56		$693.0266	$693.03	$693.05	$692.90