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	$59.81	13.233%	$67.7247	$67.72	$67.70	$67.70
Purchase #2	$72.42	8.724%	$78.7379	$78.74	$78.75	$78.70
Purchase #3	$160.82	8.680%	$174.7792	$174.78	$174.80	$174.80
Purchase #4	$214.38	5.666%	$226.5268	$226.53	$226.55	$226.50
Purchase #5	$171.78	12.156%	$192.6616	$192.66	$192.65	$192.70
Purchase #6	$203.60	13.687%	$231.4667	$231.47	$231.45	$231.50
Purchase #7	$37.70	5.744%	$39.8655	$39.87	$39.85	$39.90
7 purchase totals =	$920.51		$1,011.7624	$1,011.77	$1,011.75	$1,011.80