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	$89.95	7.793%	$96.9598	$96.96	$96.95	$97.00
Purchase #2	$164.48	3.289%	$169.8897	$169.89	$169.90	$169.90
Purchase #3	$215.41	5.553%	$227.3717	$227.37	$227.35	$227.40
Purchase #4	$49.55	10.393%	$54.6997	$54.70	$54.70	$54.70
Purchase #5	$91.81	4.491%	$95.9332	$95.93	$95.95	$95.90
Purchase #6	$106.70	4.554%	$111.5591	$111.56	$111.55	$111.60
Purchase #7	$111.91	7.330%	$120.113	$120.11	$120.10	$120.10
7 purchase totals =	$829.81		$876.5262	$876.52	$876.50	$876.60