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	$237.79	9.713%	$260.8865	$260.89	$260.90	$260.90
Purchase #2	$115.33	13.694%	$131.1233	$131.12	$131.10	$131.10
Purchase #3	$136.35	8.589%	$148.0611	$148.06	$148.05	$148.10
Purchase #4	$212.87	11.829%	$238.0504	$238.05	$238.05	$238.10
Purchase #5	$49.63	7.628%	$53.4158	$53.42	$53.40	$53.40
Purchase #6	$113.95	7.726%	$122.7538	$122.75	$122.75	$122.80
Purchase #7	$113.56	12.376%	$127.6142	$127.61	$127.60	$127.60
7 purchase totals =	$979.48		$1,081.9051	$1,081.90	$1,081.85	$1,082.00