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	$62.85	4.329%	$65.5708	$65.57	$65.55	$65.60
Purchase #2	$102.29	8.664%	$111.1524	$111.15	$111.15	$111.20
Purchase #3	$38.51	13.275%	$43.6222	$43.62	$43.60	$43.60
Purchase #4	$31.93	3.706%	$33.1133	$33.11	$33.10	$33.10
Purchase #5	$171.65	9.845%	$188.5489	$188.55	$188.55	$188.50
Purchase #6	$88.32	5.251%	$92.9577	$92.96	$92.95	$93.00
Purchase #7	$173.52	13.252%	$196.5149	$196.51	$196.50	$196.50
7 purchase totals =	$669.07		$731.4802	$731.47	$731.40	$731.50