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	$241.49	4.873%	$253.2578	$253.26	$253.25	$253.30
Purchase #2	$62.84	5.831%	$66.5042	$66.50	$66.50	$66.50
Purchase #3	$163.61	3.804%	$169.8337	$169.83	$169.85	$169.80
Purchase #4	$101.83	13.105%	$115.1748	$115.17	$115.15	$115.20
Purchase #5	$31.87	5.622%	$33.6617	$33.66	$33.65	$33.70
Purchase #6	$63.87	13.845%	$72.7128	$72.71	$72.70	$72.70
Purchase #7	$80.64	12.578%	$90.7829	$90.78	$90.80	$90.80
7 purchase totals =	$746.15		$801.9279	$801.91	$801.90	$802.00