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	$59.28	10.532%	$65.5234	$65.52	$65.50	$65.50
Purchase #2	$166.46	10.799%	$184.436	$184.44	$184.45	$184.40
Purchase #3	$12.81	3.679%	$13.2813	$13.28	$13.30	$13.30
Purchase #4	$82.59	4.317%	$86.1554	$86.16	$86.15	$86.20
Purchase #5	$184.39	5.420%	$194.3839	$194.38	$194.40	$194.40
Purchase #6	$137.52	9.512%	$150.6009	$150.60	$150.60	$150.60
Purchase #7	$38.99	6.819%	$41.6487	$41.65	$41.65	$41.60
7 purchase totals =	$682.04		$736.0296	$736.03	$736.05	$736.00