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	$46.26	13.838%	$52.6615	$52.66	$52.65	$52.70
Purchase #2	$233.25	10.870%	$258.6043	$258.60	$258.60	$258.60
Purchase #3	$23.38	4.446%	$24.4195	$24.42	$24.40	$24.40
Purchase #4	$42.56	8.749%	$46.2836	$46.28	$46.30	$46.30
Purchase #5	$183.80	8.844%	$200.0553	$200.06	$200.05	$200.10
Purchase #6	$230.82	4.794%	$241.8855	$241.89	$241.90	$241.90
Purchase #7	$171.83	5.170%	$180.7136	$180.71	$180.70	$180.70
7 purchase totals =	$931.90		$1,004.6233	$1,004.62	$1,004.60	$1,004.70