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	$222.69	6.798%	$237.8285	$237.83	$237.85	$237.80
Purchase #2	$59.91	9.541%	$65.626	$65.63	$65.65	$65.60
Purchase #3	$82.45	8.707%	$89.6289	$89.63	$89.65	$89.60
Purchase #4	$81.77	4.288%	$85.2763	$85.28	$85.30	$85.30
Purchase #5	$25.94	12.145%	$29.0904	$29.09	$29.10	$29.10
Purchase #6	$11.92	12.524%	$13.4129	$13.41	$13.40	$13.40
Purchase #7	$93.26	8.777%	$101.4454	$101.45	$101.45	$101.40
7 purchase totals =	$577.94		$622.3084	$622.32	$622.40	$622.20