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	$193.32	11.757%	$216.0486	$216.05	$216.05	$216.00
Purchase #2	$34.32	5.647%	$36.2581	$36.26	$36.25	$36.30
Purchase #3	$142.77	11.234%	$158.8088	$158.81	$158.80	$158.80
Purchase #4	$134.27	8.189%	$145.2654	$145.27	$145.25	$145.30
Purchase #5	$51.78	11.850%	$57.9159	$57.92	$57.90	$57.90
Purchase #6	$66.88	7.704%	$72.0324	$72.03	$72.05	$72.00
Purchase #7	$103.38	8.565%	$112.2345	$112.23	$112.25	$112.20
7 purchase totals =	$726.72		$798.5637	$798.57	$798.55	$798.50