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	$63.54	13.419%	$72.0664	$72.07	$72.05	$72.10
Purchase #2	$199.39	13.621%	$226.5489	$226.55	$226.55	$226.50
Purchase #3	$127.86	13.161%	$144.6877	$144.69	$144.70	$144.70
Purchase #4	$146.78	6.602%	$156.4704	$156.47	$156.45	$156.50
Purchase #5	$168.67	12.505%	$189.7622	$189.76	$189.75	$189.80
Purchase #6	$159.95	6.626%	$170.5483	$170.55	$170.55	$170.50
Purchase #7	$48.84	11.157%	$54.2891	$54.29	$54.30	$54.30
7 purchase totals =	$915.03		$1,014.3730	$1,014.38	$1,014.35	$1,014.40