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	$53.78	10.208%	$59.2699	$59.27	$59.25	$59.30
Purchase #2	$138.62	9.451%	$151.721	$151.72	$151.70	$151.70
Purchase #3	$84.65	4.552%	$88.5033	$88.50	$88.50	$88.50
Purchase #4	$199.48	9.576%	$218.5822	$218.58	$218.60	$218.60
Purchase #5	$143.83	6.453%	$153.1113	$153.11	$153.10	$153.10
Purchase #6	$209.27	13.510%	$237.5424	$237.54	$237.55	$237.50
Purchase #7	$178.29	10.413%	$196.8553	$196.86	$196.85	$196.90
7 purchase totals =	$1,007.92		$1,105.5854	$1,105.58	$1,105.55	$1,105.60