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	$208.81	8.459%	$226.4732	$226.47	$226.45	$226.50
Purchase #2	$13.29	6.284%	$14.1251	$14.13	$14.15	$14.10
Purchase #3	$27.72	12.452%	$31.1717	$31.17	$31.15	$31.20
Purchase #4	$180.65	3.246%	$186.5139	$186.51	$186.50	$186.50
Purchase #5	$129.77	7.118%	$139.007	$139.01	$139.00	$139.00
Purchase #6	$106.90	10.280%	$117.8893	$117.89	$117.90	$117.90
Purchase #7	$138.30	4.330%	$144.2884	$144.29	$144.30	$144.30
7 purchase totals =	$805.44		$859.4686	$859.47	$859.45	$859.50