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	$77.39	6.830%	$82.6757	$82.68	$82.70	$82.70
Purchase #2	$125.52	5.436%	$132.3433	$132.34	$132.35	$132.30
Purchase #3	$101.59	3.619%	$105.2665	$105.27	$105.25	$105.30
Purchase #4	$60.37	10.289%	$66.5815	$66.58	$66.60	$66.60
Purchase #5	$97.73	13.122%	$110.5541	$110.55	$110.55	$110.60
Purchase #6	$210.50	3.208%	$217.2528	$217.25	$217.25	$217.30
Purchase #7	$63.29	11.796%	$70.7557	$70.76	$70.75	$70.80
7 purchase totals =	$736.39		$785.4296	$785.43	$785.45	$785.60