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	$178.71	5.116%	$187.8528	$187.85	$187.85	$187.90
Purchase #2	$50.90	7.404%	$54.6686	$54.67	$54.65	$54.70
Purchase #3	$226.86	11.247%	$252.3749	$252.37	$252.35	$252.40
Purchase #4	$57.91	6.144%	$61.468	$61.47	$61.45	$61.50
Purchase #5	$166.38	12.611%	$187.3622	$187.36	$187.35	$187.40
Purchase #6	$123.69	8.671%	$134.4152	$134.42	$134.40	$134.40
Purchase #7	$174.79	13.136%	$197.7504	$197.75	$197.75	$197.80
7 purchase totals =	$979.24		$1,075.8921	$1,075.89	$1,075.80	$1,076.10