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	$244.34	5.290%	$257.2656	$257.27	$257.25	$257.30
Purchase #2	$104.76	6.267%	$111.3253	$111.33	$111.35	$111.30
Purchase #3	$160.25	4.553%	$167.5462	$167.55	$167.55	$167.50
Purchase #4	$43.45	3.618%	$45.022	$45.02	$45.00	$45.00
Purchase #5	$30.86	13.194%	$34.9317	$34.93	$34.95	$34.90
Purchase #6	$241.43	9.838%	$265.1819	$265.18	$265.20	$265.20
Purchase #7	$197.84	12.636%	$222.8391	$222.84	$222.85	$222.80
7 purchase totals =	$1,022.93		$1,104.1118	$1,104.12	$1,104.15	$1,104.00