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	$153.37	9.256%	$167.5659	$167.57	$167.55	$167.60
Purchase #2	$209.66	6.564%	$223.4221	$223.42	$223.40	$223.40
Purchase #3	$239.37	10.838%	$265.3129	$265.31	$265.30	$265.30
Purchase #4	$111.25	10.146%	$122.5374	$122.54	$122.55	$122.50
Purchase #5	$9.91	8.128%	$10.7155	$10.72	$10.70	$10.70
Purchase #6	$71.78	3.303%	$74.1509	$74.15	$74.15	$74.20
Purchase #7	$144.90	8.186%	$156.7615	$156.76	$156.75	$156.80
7 purchase totals =	$940.24		$1,020.4662	$1,020.47	$1,020.40	$1,020.50