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	$177.49	3.640%	$183.9506	$183.95	$183.95	$184.00
Purchase #2	$243.96	11.254%	$271.4153	$271.42	$271.40	$271.40
Purchase #3	$102.82	4.448%	$107.3934	$107.39	$107.40	$107.40
Purchase #4	$152.54	10.448%	$168.4774	$168.48	$168.50	$168.50
Purchase #5	$208.96	7.177%	$223.9571	$223.96	$223.95	$224.00
Purchase #6	$69.47	4.491%	$72.5899	$72.59	$72.60	$72.60
Purchase #7	$100.28	3.381%	$103.6705	$103.67	$103.65	$103.70
7 purchase totals =	$1,055.52		$1,131.4542	$1,131.46	$1,131.45	$1,131.60