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	$105.75	10.789%	$117.1594	$117.16	$117.15	$117.20
Purchase #2	$107.53	5.446%	$113.3861	$113.39	$113.40	$113.40
Purchase #3	$159.38	12.212%	$178.8435	$178.84	$178.85	$178.80
Purchase #4	$234.74	8.745%	$255.268	$255.27	$255.25	$255.30
Purchase #5	$85.44	4.358%	$89.1635	$89.16	$89.15	$89.20
Purchase #6	$127.25	11.323%	$141.6585	$141.66	$141.65	$141.70
Purchase #7	$104.97	8.237%	$113.6164	$113.62	$113.60	$113.60
7 purchase totals =	$925.06		$1,009.0954	$1,009.10	$1,009.05	$1,009.20