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	$72.75	7.425%	$78.1517	$78.15	$78.15	$78.20
Purchase #2	$150.45	10.636%	$166.4519	$166.45	$166.45	$166.50
Purchase #3	$103.55	7.431%	$111.2448	$111.24	$111.25	$111.20
Purchase #4	$51.77	10.821%	$57.372	$57.37	$57.35	$57.40
Purchase #5	$248.97	9.105%	$271.6387	$271.64	$271.65	$271.60
Purchase #6	$118.31	10.810%	$131.0993	$131.10	$131.10	$131.10
Purchase #7	$41.89	11.339%	$46.6399	$46.64	$46.65	$46.60
7 purchase totals =	$787.69		$862.5983	$862.59	$862.60	$862.60