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	$104.46	9.829%	$114.7274	$114.73	$114.75	$114.70
Purchase #2	$227.88	6.336%	$242.3185	$242.32	$242.30	$242.30
Purchase #3	$60.52	4.818%	$63.4359	$63.44	$63.45	$63.40
Purchase #4	$40.81	4.371%	$42.5938	$42.59	$42.60	$42.60
Purchase #5	$246.26	13.487%	$279.4731	$279.47	$279.45	$279.50
Purchase #6	$168.37	3.242%	$173.8286	$173.83	$173.85	$173.80
Purchase #7	$128.88	7.199%	$138.1581	$138.16	$138.15	$138.20
7 purchase totals =	$977.18		$1,054.5354	$1,054.54	$1,054.55	$1,054.50