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	$54.68	3.868%	$56.795	$56.80	$56.80	$56.80
Purchase #2	$117.82	8.504%	$127.8394	$127.84	$127.85	$127.80
Purchase #3	$204.28	10.113%	$224.9388	$224.94	$224.95	$224.90
Purchase #4	$67.36	10.535%	$74.4564	$74.46	$74.45	$74.50
Purchase #5	$157.38	6.513%	$167.6302	$167.63	$167.65	$167.60
Purchase #6	$54.50	12.509%	$61.3174	$61.32	$61.30	$61.30
Purchase #7	$117.61	5.122%	$123.634	$123.63	$123.65	$123.60
7 purchase totals =	$773.63		$836.6112	$836.62	$836.65	$836.50