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	$102.59	5.694%	$108.4315	$108.43	$108.45	$108.40
Purchase #2	$49.25	13.113%	$55.7082	$55.71	$55.70	$55.70
Purchase #3	$80.96	5.529%	$85.4363	$85.44	$85.45	$85.40
Purchase #4	$77.69	6.470%	$82.7165	$82.72	$82.70	$82.70
Purchase #5	$144.38	12.232%	$162.0406	$162.04	$162.05	$162.00
Purchase #6	$158.79	6.308%	$168.8065	$168.81	$168.80	$168.80
Purchase #7	$93.95	10.131%	$103.4681	$103.47	$103.45	$103.50
7 purchase totals =	$707.61		$766.6077	$766.62	$766.60	$766.50