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	$167.54	3.530%	$173.4542	$173.45	$173.45	$173.50
Purchase #2	$247.27	3.504%	$255.9343	$255.93	$255.95	$255.90
Purchase #3	$42.76	13.462%	$48.5164	$48.52	$48.50	$48.50
Purchase #4	$105.81	3.147%	$109.1398	$109.14	$109.15	$109.10
Purchase #5	$51.40	9.795%	$56.4346	$56.43	$56.45	$56.40
Purchase #6	$96.70	13.234%	$109.4973	$109.50	$109.50	$109.50
Purchase #7	$144.41	5.639%	$152.5533	$152.55	$152.55	$152.60
7 purchase totals =	$855.89		$905.5299	$905.52	$905.55	$905.50