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	$230.81	3.155%	$238.0921	$238.09	$238.10	$238.10
Purchase #2	$124.91	5.874%	$132.2472	$132.25	$132.25	$132.20
Purchase #3	$204.56	7.466%	$219.8324	$219.83	$219.85	$219.80
Purchase #4	$75.91	8.646%	$82.4732	$82.47	$82.45	$82.50
Purchase #5	$129.81	12.231%	$145.6871	$145.69	$145.70	$145.70
Purchase #6	$17.89	3.467%	$18.5102	$18.51	$18.50	$18.50
Purchase #7	$197.52	5.462%	$208.3085	$208.31	$208.30	$208.30
7 purchase totals =	$981.41		$1,045.1507	$1,045.15	$1,045.15	$1,045.10