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	$217.51	10.247%	$239.7982	$239.80	$239.80	$239.80
Purchase #2	$56.29	10.778%	$62.3569	$62.36	$62.35	$62.40
Purchase #3	$17.77	5.428%	$18.7346	$18.73	$18.75	$18.70
Purchase #4	$59.51	10.241%	$65.6044	$65.60	$65.60	$65.60
Purchase #5	$116.86	9.225%	$127.6403	$127.64	$127.65	$127.60
Purchase #6	$49.64	5.556%	$52.398	$52.40	$52.40	$52.40
Purchase #7	$248.73	6.399%	$264.6462	$264.65	$264.65	$264.60
7 purchase totals =	$766.31		$831.1786	$831.18	$831.20	$831.10