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	$216.67	10.438%	$239.286	$239.29	$239.30	$239.30
Purchase #2	$118.73	4.540%	$124.1203	$124.12	$124.10	$124.10
Purchase #3	$17.88	9.519%	$19.582	$19.58	$19.60	$19.60
Purchase #4	$89.39	6.234%	$94.9626	$94.96	$94.95	$95.00
Purchase #5	$45.83	10.124%	$50.4698	$50.47	$50.45	$50.50
Purchase #6	$43.62	6.817%	$46.5936	$46.59	$46.60	$46.60
Purchase #7	$40.59	7.227%	$43.5234	$43.52	$43.50	$43.50
7 purchase totals =	$572.71		$618.5377	$618.53	$618.50	$618.60