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	$11.33	11.670%	$12.6522	$12.65	$12.65	$12.70
Purchase #2	$183.87	9.274%	$200.9221	$200.92	$200.90	$200.90
Purchase #3	$115.57	10.134%	$127.2819	$127.28	$127.30	$127.30
Purchase #4	$243.37	8.725%	$264.604	$264.60	$264.60	$264.60
Purchase #5	$158.39	10.330%	$174.7517	$174.75	$174.75	$174.80
Purchase #6	$108.33	3.229%	$111.828	$111.83	$111.85	$111.80
Purchase #7	$210.84	11.395%	$234.8652	$234.87	$234.85	$234.90
7 purchase totals =	$1,031.70		$1,126.9051	$1,126.90	$1,126.90	$1,127.00