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	$241.63	3.760%	$250.7153	$250.72	$250.70	$250.70
Purchase #2	$40.51	4.287%	$42.2467	$42.25	$42.25	$42.20
Purchase #3	$122.79	12.791%	$138.4961	$138.50	$138.50	$138.50
Purchase #4	$130.40	11.370%	$145.2265	$145.23	$145.25	$145.20
Purchase #5	$120.65	4.660%	$126.2723	$126.27	$126.25	$126.30
Purchase #6	$128.97	12.128%	$144.6115	$144.61	$144.60	$144.60
Purchase #7	$212.64	5.285%	$223.878	$223.88	$223.90	$223.90
7 purchase totals =	$997.59		$1,071.4464	$1,071.46	$1,071.45	$1,071.40