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	$120.88	5.338%	$127.3326	$127.33	$127.35	$127.30
Purchase #2	$127.38	9.610%	$139.6212	$139.62	$139.60	$139.60
Purchase #3	$56.66	5.209%	$59.6114	$59.61	$59.60	$59.60
Purchase #4	$137.92	13.489%	$156.524	$156.52	$156.50	$156.50
Purchase #5	$81.33	6.229%	$86.396	$86.40	$86.40	$86.40
Purchase #6	$132.32	6.420%	$140.8149	$140.81	$140.80	$140.80
Purchase #7	$70.79	4.762%	$74.161	$74.16	$74.15	$74.20
7 purchase totals =	$727.28		$784.4611	$784.45	$784.40	$784.40