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	$116.43	9.205%	$127.1474	$127.15	$127.15	$127.10
Purchase #2	$160.95	13.327%	$182.3998	$182.40	$182.40	$182.40
Purchase #3	$172.34	12.792%	$194.3857	$194.39	$194.40	$194.40
Purchase #4	$53.83	13.105%	$60.8844	$60.88	$60.90	$60.90
Purchase #5	$62.95	3.516%	$65.1633	$65.16	$65.15	$65.20
Purchase #6	$40.70	3.729%	$42.2177	$42.22	$42.20	$42.20
Purchase #7	$61.88	10.273%	$68.2369	$68.24	$68.25	$68.20
7 purchase totals =	$669.08		$740.4352	$740.44	$740.45	$740.40