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	$235.73	13.466%	$267.4734	$267.47	$267.45	$267.50
Purchase #2	$218.39	4.110%	$227.3658	$227.37	$227.35	$227.40
Purchase #3	$153.75	12.864%	$173.5284	$173.53	$173.55	$173.50
Purchase #4	$69.49	12.589%	$78.2381	$78.24	$78.25	$78.20
Purchase #5	$148.48	12.416%	$166.9153	$166.92	$166.90	$166.90
Purchase #6	$111.50	13.294%	$126.3228	$126.32	$126.30	$126.30
Purchase #7	$26.90	7.124%	$28.8164	$28.82	$28.80	$28.80
7 purchase totals =	$964.24		$1,068.6602	$1,068.67	$1,068.60	$1,068.60