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	$151.27	10.422%	$167.0354	$167.04	$167.05	$167.00
Purchase #2	$69.37	5.150%	$72.9426	$72.94	$72.95	$72.90
Purchase #3	$153.48	4.314%	$160.1011	$160.10	$160.10	$160.10
Purchase #4	$50.54	7.571%	$54.3664	$54.37	$54.35	$54.40
Purchase #5	$74.70	7.213%	$80.0881	$80.09	$80.10	$80.10
Purchase #6	$198.34	7.190%	$212.6006	$212.60	$212.60	$212.60
Purchase #7	$25.84	10.266%	$28.4927	$28.49	$28.50	$28.50
7 purchase totals =	$723.54		$775.6269	$775.63	$775.65	$775.60