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	$78.38	11.826%	$87.6492	$87.65	$87.65	$87.60
Purchase #2	$158.48	5.293%	$166.8683	$166.87	$166.85	$166.90
Purchase #3	$94.47	5.522%	$99.6866	$99.69	$99.70	$99.70
Purchase #4	$247.42	3.214%	$255.3721	$255.37	$255.35	$255.40
Purchase #5	$73.70	4.177%	$76.7784	$76.78	$76.80	$76.80
Purchase #6	$226.54	11.660%	$252.9546	$252.95	$252.95	$253.00
Purchase #7	$145.38	4.172%	$151.4453	$151.45	$151.45	$151.40
7 purchase totals =	$1,024.37		$1,090.7545	$1,090.76	$1,090.75	$1,090.80