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	$127.82	5.338%	$134.643	$134.64	$134.65	$134.60
Purchase #2	$161.89	7.862%	$174.6178	$174.62	$174.60	$174.60
Purchase #3	$35.28	9.298%	$38.5603	$38.56	$38.55	$38.60
Purchase #4	$96.75	3.662%	$100.293	$100.29	$100.30	$100.30
Purchase #5	$183.26	7.530%	$197.0595	$197.06	$197.05	$197.10
Purchase #6	$179.91	9.422%	$196.8611	$196.86	$196.85	$196.90
Purchase #7	$90.32	9.536%	$98.9329	$98.93	$98.95	$98.90
7 purchase totals =	$875.23		$940.9676	$940.96	$940.95	$941.00