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	$166.88	6.409%	$177.5753	$177.58	$177.60	$177.60
Purchase #2	$94.88	6.310%	$100.8669	$100.87	$100.85	$100.90
Purchase #3	$134.34	12.370%	$150.9579	$150.96	$150.95	$151.00
Purchase #4	$108.36	3.169%	$111.7939	$111.79	$111.80	$111.80
Purchase #5	$205.69	9.614%	$225.465	$225.47	$225.45	$225.50
Purchase #6	$213.50	11.247%	$237.5123	$237.51	$237.50	$237.50
Purchase #7	$185.95	13.747%	$211.5125	$211.51	$211.50	$211.50
7 purchase totals =	$1,109.60		$1,215.6838	$1,215.69	$1,215.65	$1,215.80