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	$119.92	9.348%	$131.1301	$131.13	$131.15	$131.10
Purchase #2	$141.33	3.755%	$146.6369	$146.64	$146.65	$146.60
Purchase #3	$247.95	12.156%	$278.0908	$278.09	$278.10	$278.10
Purchase #4	$112.95	12.651%	$127.2393	$127.24	$127.25	$127.20
Purchase #5	$113.70	9.383%	$124.3685	$124.37	$124.35	$124.40
Purchase #6	$166.92	12.269%	$187.3994	$187.40	$187.40	$187.40
Purchase #7	$164.91	4.451%	$172.2501	$172.25	$172.25	$172.30
7 purchase totals =	$1,067.68		$1,167.1151	$1,167.12	$1,167.15	$1,167.10