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	$58.67	3.666%	$60.8208	$60.82	$60.80	$60.80
Purchase #2	$48.81	5.361%	$51.4267	$51.43	$51.45	$51.40
Purchase #3	$28.38	13.526%	$32.2187	$32.22	$32.20	$32.20
Purchase #4	$212.65	13.832%	$242.0637	$242.06	$242.05	$242.10
Purchase #5	$104.82	7.414%	$112.5914	$112.59	$112.60	$112.60
Purchase #6	$133.55	6.260%	$141.9102	$141.91	$141.90	$141.90
Purchase #7	$20.49	6.220%	$21.7645	$21.76	$21.75	$21.80
7 purchase totals =	$607.37		$662.7960	$662.79	$662.75	$662.80