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	$139.45	10.533%	$154.1383	$154.14	$154.15	$154.10
Purchase #2	$21.82	10.532%	$24.1181	$24.12	$24.10	$24.10
Purchase #3	$89.64	3.204%	$92.5121	$92.51	$92.50	$92.50
Purchase #4	$112.52	9.832%	$123.583	$123.58	$123.60	$123.60
Purchase #5	$138.80	4.667%	$145.2778	$145.28	$145.30	$145.30
Purchase #6	$139.52	5.439%	$147.1085	$147.11	$147.10	$147.10
Purchase #7	$106.67	5.773%	$112.8281	$112.83	$112.85	$112.80
7 purchase totals =	$748.42		$799.5659	$799.57	$799.60	$799.50