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	$164.73	10.760%	$182.4549	$182.45	$182.45	$182.50
Purchase #2	$225.51	13.466%	$255.8772	$255.88	$255.90	$255.90
Purchase #3	$118.90	8.377%	$128.8603	$128.86	$128.85	$128.90
Purchase #4	$111.56	5.733%	$117.9557	$117.96	$117.95	$118.00
Purchase #5	$169.37	12.670%	$190.8292	$190.83	$190.85	$190.80
Purchase #6	$179.99	3.819%	$186.8638	$186.86	$186.85	$186.90
Purchase #7	$115.77	8.176%	$125.2354	$125.24	$125.25	$125.20
7 purchase totals =	$1,085.83		$1,188.0765	$1,188.08	$1,188.10	$1,188.20