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	$204.60	8.648%	$222.2938	$222.29	$222.30	$222.30
Purchase #2	$182.38	12.812%	$205.7465	$205.75	$205.75	$205.70
Purchase #3	$222.74	10.210%	$245.4818	$245.48	$245.50	$245.50
Purchase #4	$99.82	4.656%	$104.4676	$104.47	$104.45	$104.50
Purchase #5	$134.95	6.748%	$144.0564	$144.06	$144.05	$144.10
Purchase #6	$212.69	12.261%	$238.7679	$238.77	$238.75	$238.80
Purchase #7	$100.32	3.467%	$103.7981	$103.80	$103.80	$103.80
7 purchase totals =	$1,157.50		$1,264.6121	$1,264.62	$1,264.60	$1,264.70