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	$168.59	5.149%	$177.2707	$177.27	$177.25	$177.30
Purchase #2	$56.62	10.736%	$62.6987	$62.70	$62.70	$62.70
Purchase #3	$10.29	13.114%	$11.6394	$11.64	$11.65	$11.60
Purchase #4	$158.47	13.213%	$179.4086	$179.41	$179.40	$179.40
Purchase #5	$148.50	5.113%	$156.0928	$156.09	$156.10	$156.10
Purchase #6	$247.25	11.404%	$275.4464	$275.45	$275.45	$275.40
Purchase #7	$142.79	8.582%	$155.0442	$155.04	$155.05	$155.00
7 purchase totals =	$932.51		$1,017.6008	$1,017.60	$1,017.60	$1,017.50