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	$108.89	7.842%	$117.4292	$117.43	$117.45	$117.40
Purchase #2	$117.91	7.798%	$127.1046	$127.10	$127.10	$127.10
Purchase #3	$34.86	5.517%	$36.7832	$36.78	$36.80	$36.80
Purchase #4	$70.80	10.561%	$78.2772	$78.28	$78.30	$78.30
Purchase #5	$18.92	12.783%	$21.3385	$21.34	$21.35	$21.30
Purchase #6	$106.99	5.233%	$112.5888	$112.59	$112.60	$112.60
Purchase #7	$118.69	6.474%	$126.374	$126.37	$126.35	$126.40
7 purchase totals =	$577.06		$619.8955	$619.89	$619.95	$619.90