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	$176.52	9.248%	$192.8446	$192.84	$192.85	$192.80
Purchase #2	$250.26	3.534%	$259.1042	$259.10	$259.10	$259.10
Purchase #3	$86.30	4.123%	$89.8581	$89.86	$89.85	$89.90
Purchase #4	$26.59	8.370%	$28.8156	$28.82	$28.80	$28.80
Purchase #5	$119.61	5.720%	$126.4517	$126.45	$126.45	$126.50
Purchase #6	$38.68	4.403%	$40.3831	$40.38	$40.40	$40.40
Purchase #7	$153.37	5.748%	$162.1857	$162.19	$162.20	$162.20
7 purchase totals =	$851.33		$899.6430	$899.64	$899.65	$899.70