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	$211.85	13.428%	$240.2972	$240.30	$240.30	$240.30
Purchase #2	$33.64	9.338%	$36.7813	$36.78	$36.80	$36.80
Purchase #3	$143.81	11.803%	$160.7839	$160.78	$160.80	$160.80
Purchase #4	$18.72	3.281%	$19.3342	$19.33	$19.35	$19.30
Purchase #5	$198.83	9.233%	$217.188	$217.19	$217.20	$217.20
Purchase #6	$243.27	4.848%	$255.0637	$255.06	$255.05	$255.10
Purchase #7	$212.58	12.234%	$238.587	$238.59	$238.60	$238.60
7 purchase totals =	$1,062.70		$1,168.0353	$1,168.03	$1,168.10	$1,168.10