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	$110.53	11.854%	$123.6322	$123.63	$123.65	$123.60
Purchase #2	$226.32	13.521%	$256.9207	$256.92	$256.90	$256.90
Purchase #3	$120.80	5.214%	$127.0985	$127.10	$127.10	$127.10
Purchase #4	$117.90	9.261%	$128.8187	$128.82	$128.80	$128.80
Purchase #5	$33.70	5.115%	$35.4238	$35.42	$35.40	$35.40
Purchase #6	$38.60	12.130%	$43.2822	$43.28	$43.30	$43.30
Purchase #7	$27.46	6.383%	$29.2128	$29.21	$29.20	$29.20
7 purchase totals =	$675.31		$744.3889	$744.38	$744.35	$744.30