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	$173.41	4.206%	$180.7036	$180.70	$180.70	$180.70
Purchase #2	$33.98	7.413%	$36.4989	$36.50	$36.50	$36.50
Purchase #3	$118.71	4.305%	$123.8205	$123.82	$123.80	$123.80
Purchase #4	$221.28	4.422%	$231.065	$231.07	$231.05	$231.10
Purchase #5	$243.54	5.656%	$257.3146	$257.31	$257.30	$257.30
Purchase #6	$210.60	12.208%	$236.31	$236.31	$236.30	$236.30
Purchase #7	$95.36	10.563%	$105.4329	$105.43	$105.45	$105.40
7 purchase totals =	$1,096.88		$1,171.1455	$1,171.14	$1,171.10	$1,171.10