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	$244.77	8.378%	$265.2768	$265.28	$265.30	$265.30
Purchase #2	$124.94	10.139%	$137.6077	$137.61	$137.60	$137.60
Purchase #3	$22.78	6.344%	$24.2252	$24.23	$24.25	$24.20
Purchase #4	$83.39	7.626%	$89.7493	$89.75	$89.75	$89.70
Purchase #5	$142.97	5.388%	$150.6732	$150.67	$150.65	$150.70
Purchase #6	$227.49	4.472%	$237.6634	$237.66	$237.65	$237.70
Purchase #7	$173.59	4.655%	$181.6706	$181.67	$181.65	$181.70
7 purchase totals =	$1,019.93		$1,086.8662	$1,086.87	$1,086.85	$1,086.90