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	$223.94	10.529%	$247.5186	$247.52	$247.50	$247.50
Purchase #2	$237.38	7.611%	$255.447	$255.45	$255.45	$255.40
Purchase #3	$235.67	10.443%	$260.281	$260.28	$260.30	$260.30
Purchase #4	$117.79	12.441%	$132.4443	$132.44	$132.45	$132.40
Purchase #5	$134.77	12.124%	$151.1095	$151.11	$151.10	$151.10
Purchase #6	$74.91	4.177%	$78.039	$78.04	$78.05	$78.00
Purchase #7	$53.72	7.195%	$57.5852	$57.59	$57.60	$57.60
7 purchase totals =	$1,078.18		$1,182.4246	$1,182.43	$1,182.45	$1,182.30