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	$151.70	10.487%	$167.6088	$167.61	$167.60	$167.60
Purchase #2	$230.58	11.579%	$257.2789	$257.28	$257.30	$257.30
Purchase #3	$105.48	10.405%	$116.4552	$116.46	$116.45	$116.50
Purchase #4	$47.61	8.275%	$51.5497	$51.55	$51.55	$51.50
Purchase #5	$29.59	3.664%	$30.6742	$30.67	$30.65	$30.70
Purchase #6	$223.78	9.179%	$244.3208	$244.32	$244.30	$244.30
Purchase #7	$166.27	13.301%	$188.3856	$188.39	$188.40	$188.40
7 purchase totals =	$955.01		$1,056.2732	$1,056.28	$1,056.25	$1,056.30