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	$52.54	3.739%	$54.5045	$54.50	$54.50	$54.50
Purchase #2	$149.28	4.765%	$156.3932	$156.39	$156.40	$156.40
Purchase #3	$79.74	5.380%	$84.03	$84.03	$84.05	$84.00
Purchase #4	$74.64	10.617%	$82.5645	$82.56	$82.55	$82.60
Purchase #5	$171.57	4.582%	$179.4313	$179.43	$179.45	$179.40
Purchase #6	$177.90	6.624%	$189.6841	$189.68	$189.70	$189.70
Purchase #7	$177.66	13.108%	$200.9477	$200.95	$200.95	$200.90
7 purchase totals =	$883.33		$947.5553	$947.54	$947.60	$947.50