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	$213.81	11.236%	$237.8337	$237.83	$237.85	$237.80
Purchase #2	$13.98	11.744%	$15.6218	$15.62	$15.60	$15.60
Purchase #3	$108.58	5.229%	$114.2576	$114.26	$114.25	$114.30
Purchase #4	$78.42	4.656%	$82.0712	$82.07	$82.05	$82.10
Purchase #5	$6.25	4.365%	$6.5228	$6.52	$6.50	$6.50
Purchase #6	$68.67	4.743%	$71.927	$71.93	$71.95	$71.90
Purchase #7	$107.68	9.666%	$118.0883	$118.09	$118.10	$118.10
7 purchase totals =	$597.39		$646.3224	$646.32	$646.30	$646.30