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	$103.43	13.497%	$117.3899	$117.39	$117.40	$117.40
Purchase #2	$147.42	4.833%	$154.5448	$154.54	$154.55	$154.50
Purchase #3	$235.41	12.450%	$264.7185	$264.72	$264.70	$264.70
Purchase #4	$127.49	9.240%	$139.2701	$139.27	$139.25	$139.30
Purchase #5	$17.31	7.406%	$18.592	$18.59	$18.60	$18.60
Purchase #6	$155.33	3.281%	$160.4264	$160.43	$160.45	$160.40
Purchase #7	$241.60	5.615%	$255.1658	$255.17	$255.15	$255.20
7 purchase totals =	$1,027.99		$1,110.1075	$1,110.11	$1,110.10	$1,110.10