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	$43.54	11.227%	$48.4282	$48.43	$48.45	$48.40
Purchase #2	$214.31	7.232%	$229.8089	$229.81	$229.80	$229.80
Purchase #3	$123.76	6.750%	$132.1138	$132.11	$132.10	$132.10
Purchase #4	$39.63	10.230%	$43.6841	$43.68	$43.70	$43.70
Purchase #5	$16.62	4.502%	$17.3682	$17.37	$17.35	$17.40
Purchase #6	$78.55	5.358%	$82.7587	$82.76	$82.75	$82.80
Purchase #7	$109.51	3.149%	$112.9585	$112.96	$112.95	$113.00
7 purchase totals =	$625.92		$667.1204	$667.12	$667.10	$667.20