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	$188.92	8.858%	$205.6545	$205.65	$205.65	$205.70
Purchase #2	$7.55	11.647%	$8.4293	$8.43	$8.45	$8.40
Purchase #3	$165.40	13.414%	$187.5868	$187.59	$187.60	$187.60
Purchase #4	$237.37	9.303%	$259.4525	$259.45	$259.45	$259.50
Purchase #5	$111.54	5.207%	$117.3479	$117.35	$117.35	$117.30
Purchase #6	$73.28	7.180%	$78.5415	$78.54	$78.55	$78.50
Purchase #7	$235.41	10.132%	$259.2617	$259.26	$259.25	$259.30
7 purchase totals =	$1,019.47		$1,116.2742	$1,116.27	$1,116.30	$1,116.30