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	$200.78	4.361%	$209.536	$209.54	$209.55	$209.50
Purchase #2	$75.60	7.794%	$81.4923	$81.49	$81.50	$81.50
Purchase #3	$245.42	5.572%	$259.0948	$259.09	$259.10	$259.10
Purchase #4	$155.78	10.730%	$172.4952	$172.50	$172.50	$172.50
Purchase #5	$142.28	11.873%	$159.1729	$159.17	$159.15	$159.20
Purchase #6	$116.53	9.387%	$127.4687	$127.47	$127.45	$127.50
Purchase #7	$227.57	7.681%	$245.0497	$245.05	$245.05	$245.00
7 purchase totals =	$1,163.96		$1,254.3096	$1,254.31	$1,254.30	$1,254.30