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	$99.95	11.773%	$111.7171	$111.72	$111.70	$111.70
Purchase #2	$23.61	5.747%	$24.9669	$24.97	$24.95	$25.00
Purchase #3	$248.33	8.555%	$269.5746	$269.57	$269.55	$269.60
Purchase #4	$44.33	7.548%	$47.676	$47.68	$47.70	$47.70
Purchase #5	$189.27	12.301%	$212.5521	$212.55	$212.55	$212.60
Purchase #6	$233.89	10.575%	$258.6239	$258.62	$258.60	$258.60
Purchase #7	$139.28	5.167%	$146.4766	$146.48	$146.50	$146.50
7 purchase totals =	$978.66		$1,071.5872	$1,071.59	$1,071.55	$1,071.70