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	$186.95	5.108%	$196.4994	$196.50	$196.50	$196.50
Purchase #2	$15.94	8.214%	$17.2493	$17.25	$17.25	$17.20
Purchase #3	$135.45	6.169%	$143.8059	$143.81	$143.80	$143.80
Purchase #4	$25.97	4.470%	$27.1309	$27.13	$27.15	$27.10
Purchase #5	$59.58	6.116%	$63.2239	$63.22	$63.20	$63.20
Purchase #6	$65.89	9.704%	$72.284	$72.28	$72.30	$72.30
Purchase #7	$46.82	13.684%	$53.2268	$53.23	$53.25	$53.20
7 purchase totals =	$536.60		$573.4202	$573.42	$573.45	$573.30