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	$45.26	9.401%	$49.5149	$49.51	$49.50	$49.50
Purchase #2	$46.25	9.634%	$50.7057	$50.71	$50.70	$50.70
Purchase #3	$154.32	13.724%	$175.4989	$175.50	$175.50	$175.50
Purchase #4	$46.86	10.228%	$51.6528	$51.65	$51.65	$51.70
Purchase #5	$143.61	4.545%	$150.1371	$150.14	$150.15	$150.10
Purchase #6	$43.59	8.607%	$47.3418	$47.34	$47.35	$47.30
Purchase #7	$211.67	10.364%	$233.6075	$233.61	$233.60	$233.60
7 purchase totals =	$691.56		$758.4587	$758.46	$758.45	$758.40