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	$105.39	5.744%	$111.4436	$111.44	$111.45	$111.40
Purchase #2	$183.74	9.328%	$200.8793	$200.88	$200.90	$200.90
Purchase #3	$54.52	5.247%	$57.3807	$57.38	$57.40	$57.40
Purchase #4	$17.59	13.802%	$20.0178	$20.02	$20.00	$20.00
Purchase #5	$54.54	10.399%	$60.2116	$60.21	$60.20	$60.20
Purchase #6	$230.97	3.431%	$238.8946	$238.89	$238.90	$238.90
Purchase #7	$20.92	4.710%	$21.9053	$21.91	$21.90	$21.90
7 purchase totals =	$667.67		$710.7329	$710.73	$710.75	$710.70