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	$122.85	7.685%	$132.291	$132.29	$132.30	$132.30
Purchase #2	$100.77	12.553%	$113.4197	$113.42	$113.40	$113.40
Purchase #3	$110.59	9.792%	$121.419	$121.42	$121.40	$121.40
Purchase #4	$77.69	9.454%	$85.0348	$85.03	$85.05	$85.00
Purchase #5	$101.43	9.584%	$111.1511	$111.15	$111.15	$111.20
Purchase #6	$74.42	5.264%	$78.3375	$78.34	$78.35	$78.30
Purchase #7	$102.59	8.864%	$111.6836	$111.68	$111.70	$111.70
7 purchase totals =	$690.34		$753.3367	$753.33	$753.35	$753.30