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	$153.76	7.187%	$164.8107	$164.81	$164.80	$164.80
Purchase #2	$60.70	7.286%	$65.1226	$65.12	$65.10	$65.10
Purchase #3	$9.96	5.520%	$10.5098	$10.51	$10.50	$10.50
Purchase #4	$205.88	13.582%	$233.8426	$233.84	$233.85	$233.80
Purchase #5	$239.40	4.823%	$250.9463	$250.95	$250.95	$250.90
Purchase #6	$136.65	6.436%	$145.4448	$145.44	$145.45	$145.40
Purchase #7	$95.34	13.563%	$108.271	$108.27	$108.25	$108.30
7 purchase totals =	$901.69		$978.9478	$978.94	$978.90	$978.80