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	$48.65	11.751%	$54.3669	$54.37	$54.35	$54.40
Purchase #2	$57.78	12.600%	$65.0603	$65.06	$65.05	$65.10
Purchase #3	$19.63	7.407%	$21.084	$21.08	$21.10	$21.10
Purchase #4	$223.61	13.824%	$254.5218	$254.52	$254.50	$254.50
Purchase #5	$202.55	5.682%	$214.0589	$214.06	$214.05	$214.10
Purchase #6	$247.49	10.491%	$273.4542	$273.45	$273.45	$273.50
Purchase #7	$208.94	3.591%	$216.443	$216.44	$216.45	$216.40
7 purchase totals =	$1,008.65		$1,098.9891	$1,098.98	$1,098.95	$1,099.10