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	$41.86	4.858%	$43.8936	$43.89	$43.90	$43.90
Purchase #2	$58.89	13.464%	$66.8189	$66.82	$66.80	$66.80
Purchase #3	$15.56	3.737%	$16.1415	$16.14	$16.15	$16.10
Purchase #4	$236.25	13.305%	$267.6831	$267.68	$267.70	$267.70
Purchase #5	$107.77	10.786%	$119.3941	$119.39	$119.40	$119.40
Purchase #6	$217.88	3.420%	$225.3315	$225.33	$225.35	$225.30
Purchase #7	$119.31	6.503%	$127.0687	$127.07	$127.05	$127.10
7 purchase totals =	$797.52		$866.3314	$866.32	$866.35	$866.30