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	$63.30	11.699%	$70.7055	$70.71	$70.70	$70.70
Purchase #2	$31.73	6.458%	$33.7791	$33.78	$33.80	$33.80
Purchase #3	$78.71	13.550%	$89.3752	$89.38	$89.40	$89.40
Purchase #4	$11.52	5.801%	$12.1883	$12.19	$12.20	$12.20
Purchase #5	$149.61	7.143%	$160.2966	$160.30	$160.30	$160.30
Purchase #6	$238.60	12.757%	$269.0382	$269.04	$269.05	$269.00
Purchase #7	$250.60	7.583%	$269.603	$269.60	$269.60	$269.60
7 purchase totals =	$824.07		$904.9859	$905.00	$905.05	$905.00