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	$72.93	7.646%	$78.5062	$78.51	$78.50	$78.50
Purchase #2	$66.38	3.719%	$68.8487	$68.85	$68.85	$68.80
Purchase #3	$77.57	5.708%	$81.9977	$82.00	$82.00	$82.00
Purchase #4	$190.40	12.607%	$214.4037	$214.40	$214.40	$214.40
Purchase #5	$199.97	3.748%	$207.4649	$207.46	$207.45	$207.50
Purchase #6	$112.30	13.686%	$127.6694	$127.67	$127.65	$127.70
Purchase #7	$168.85	10.383%	$186.3817	$186.38	$186.40	$186.40
7 purchase totals =	$888.40		$965.2723	$965.27	$965.25	$965.30