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	$94.78	10.852%	$105.0655	$105.07	$105.05	$105.10
Purchase #2	$79.63	12.383%	$89.4906	$89.49	$89.50	$89.50
Purchase #3	$112.86	9.245%	$123.2939	$123.29	$123.30	$123.30
Purchase #4	$34.67	9.761%	$38.0541	$38.05	$38.05	$38.10
Purchase #5	$84.60	3.333%	$87.4197	$87.42	$87.40	$87.40
Purchase #6	$84.88	5.684%	$89.7046	$89.70	$89.70	$89.70
Purchase #7	$134.42	13.123%	$152.0599	$152.06	$152.05	$152.10
7 purchase totals =	$625.84		$685.0883	$685.08	$685.05	$685.20