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	$95.39	5.713%	$100.8396	$100.84	$100.85	$100.80
Purchase #2	$154.60	12.513%	$173.9451	$173.95	$173.95	$173.90
Purchase #3	$50.64	6.121%	$53.7397	$53.74	$53.75	$53.70
Purchase #4	$73.51	9.595%	$80.5633	$80.56	$80.55	$80.60
Purchase #5	$154.56	11.787%	$172.778	$172.78	$172.80	$172.80
Purchase #6	$208.78	7.745%	$224.95	$224.95	$224.95	$225.00
Purchase #7	$139.96	13.251%	$158.5061	$158.51	$158.50	$158.50
7 purchase totals =	$877.44		$965.3218	$965.33	$965.35	$965.30