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	$238.74	10.436%	$263.6549	$263.65	$263.65	$263.70
Purchase #2	$71.72	9.335%	$78.4151	$78.42	$78.40	$78.40
Purchase #3	$40.42	12.397%	$45.4309	$45.43	$45.45	$45.40
Purchase #4	$186.42	5.504%	$196.6806	$196.68	$196.70	$196.70
Purchase #5	$95.39	12.605%	$107.4139	$107.41	$107.40	$107.40
Purchase #6	$232.93	7.596%	$250.6234	$250.62	$250.60	$250.60
Purchase #7	$127.81	6.209%	$135.7457	$135.75	$135.75	$135.70
7 purchase totals =	$993.43		$1,077.9645	$1,077.96	$1,077.95	$1,077.90