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	$153.28	13.259%	$173.6034	$173.60	$173.60	$173.60
Purchase #2	$203.77	13.196%	$230.6595	$230.66	$230.65	$230.70
Purchase #3	$231.29	5.655%	$244.3694	$244.37	$244.35	$244.40
Purchase #4	$123.88	5.285%	$130.4271	$130.43	$130.45	$130.40
Purchase #5	$68.37	12.465%	$76.8923	$76.89	$76.90	$76.90
Purchase #6	$81.70	8.312%	$88.4909	$88.49	$88.50	$88.50
Purchase #7	$100.78	4.800%	$105.6174	$105.62	$105.60	$105.60
7 purchase totals =	$963.07		$1,050.0600	$1,050.06	$1,050.05	$1,050.10