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	$241.37	3.534%	$249.9	$249.90	$249.90	$249.90
Purchase #2	$181.27	10.612%	$200.5064	$200.51	$200.50	$200.50
Purchase #3	$105.68	12.697%	$119.0982	$119.10	$119.10	$119.10
Purchase #4	$66.26	10.603%	$73.2855	$73.29	$73.30	$73.30
Purchase #5	$176.27	7.607%	$189.6789	$189.68	$189.70	$189.70
Purchase #6	$106.60	12.409%	$119.828	$119.83	$119.85	$119.80
Purchase #7	$121.92	10.109%	$134.2449	$134.24	$134.25	$134.20
7 purchase totals =	$999.37		$1,086.5419	$1,086.55	$1,086.60	$1,086.50