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	$238.71	11.106%	$265.2211	$265.22	$265.20	$265.20
Purchase #2	$223.39	10.474%	$246.7879	$246.79	$246.80	$246.80
Purchase #3	$107.65	3.463%	$111.3779	$111.38	$111.40	$111.40
Purchase #4	$212.93	3.605%	$220.6061	$220.61	$220.60	$220.60
Purchase #5	$127.41	10.185%	$140.3867	$140.39	$140.40	$140.40
Purchase #6	$47.59	13.247%	$53.8942	$53.89	$53.90	$53.90
Purchase #7	$49.72	11.510%	$55.4428	$55.44	$55.45	$55.40
7 purchase totals =	$1,007.40		$1,093.7167	$1,093.72	$1,093.75	$1,093.70