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	$46.31	3.768%	$48.055	$48.06	$48.05	$48.10
Purchase #2	$227.45	6.661%	$242.6004	$242.60	$242.60	$242.60
Purchase #3	$209.50	7.469%	$225.1476	$225.15	$225.15	$225.10
Purchase #4	$232.37	5.364%	$244.8343	$244.83	$244.85	$244.80
Purchase #5	$71.72	12.841%	$80.9296	$80.93	$80.95	$80.90
Purchase #6	$114.28	11.754%	$127.7125	$127.71	$127.70	$127.70
Purchase #7	$90.92	10.671%	$100.6221	$100.62	$100.60	$100.60
7 purchase totals =	$992.55		$1,069.9015	$1,069.90	$1,069.90	$1,069.80