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	$206.90	4.191%	$215.5712	$215.57	$215.55	$215.60
Purchase #2	$132.86	4.400%	$138.7058	$138.71	$138.70	$138.70
Purchase #3	$83.52	10.398%	$92.2044	$92.20	$92.20	$92.20
Purchase #4	$128.25	10.392%	$141.5777	$141.58	$141.60	$141.60
Purchase #5	$100.52	11.275%	$111.8536	$111.85	$111.85	$111.90
Purchase #6	$218.34	8.813%	$237.5823	$237.58	$237.60	$237.60
Purchase #7	$77.40	5.552%	$81.6972	$81.70	$81.70	$81.70
7 purchase totals =	$947.79		$1,019.1922	$1,019.19	$1,019.20	$1,019.30