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	$53.42	6.392%	$56.8346	$56.83	$56.85	$56.80
Purchase #2	$151.30	13.829%	$172.2233	$172.22	$172.20	$172.20
Purchase #3	$222.44	13.338%	$252.109	$252.11	$252.10	$252.10
Purchase #4	$142.65	9.293%	$155.9065	$155.91	$155.90	$155.90
Purchase #5	$223.43	6.466%	$237.877	$237.88	$237.90	$237.90
Purchase #6	$156.86	6.356%	$166.83	$166.83	$166.85	$166.80
Purchase #7	$102.30	10.284%	$112.8205	$112.82	$112.80	$112.80
7 purchase totals =	$1,052.40		$1,154.6009	$1,154.60	$1,154.60	$1,154.50