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	$118.57	3.751%	$123.0176	$123.02	$123.00	$123.00
Purchase #2	$233.95	10.326%	$258.1077	$258.11	$258.10	$258.10
Purchase #3	$32.63	11.157%	$36.2705	$36.27	$36.25	$36.30
Purchase #4	$185.60	4.284%	$193.5511	$193.55	$193.55	$193.60
Purchase #5	$154.67	8.498%	$167.8139	$167.81	$167.80	$167.80
Purchase #6	$215.88	10.684%	$238.9446	$238.94	$238.95	$238.90
Purchase #7	$93.65	12.724%	$105.566	$105.57	$105.55	$105.60
7 purchase totals =	$1,034.95		$1,123.2714	$1,123.27	$1,123.20	$1,123.30