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	$79.73	13.806%	$90.7375	$90.74	$90.75	$90.70
Purchase #2	$164.81	4.697%	$172.5511	$172.55	$172.55	$172.60
Purchase #3	$170.29	6.402%	$181.192	$181.19	$181.20	$181.20
Purchase #4	$13.90	11.163%	$15.4517	$15.45	$15.45	$15.50
Purchase #5	$184.85	12.264%	$207.52	$207.52	$207.50	$207.50
Purchase #6	$43.72	6.523%	$46.5719	$46.57	$46.55	$46.60
Purchase #7	$158.59	9.273%	$173.2961	$173.30	$173.30	$173.30
7 purchase totals =	$815.89		$887.3203	$887.32	$887.30	$887.40