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	$81.32	11.658%	$90.8003	$90.80	$90.80	$90.80
Purchase #2	$10.62	5.424%	$11.196	$11.20	$11.20	$11.20
Purchase #3	$36.59	10.102%	$40.2863	$40.29	$40.30	$40.30
Purchase #4	$43.76	9.159%	$47.768	$47.77	$47.75	$47.80
Purchase #5	$48.52	8.373%	$52.5826	$52.58	$52.60	$52.60
Purchase #6	$96.62	9.298%	$105.6037	$105.60	$105.60	$105.60
Purchase #7	$90.65	6.338%	$96.3954	$96.40	$96.40	$96.40
7 purchase totals =	$408.08		$444.6323	$444.64	$444.65	$444.70