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	$128.42	13.359%	$145.5756	$145.58	$145.60	$145.60
Purchase #2	$106.54	10.353%	$117.5701	$117.57	$117.55	$117.60
Purchase #3	$116.43	11.871%	$130.2514	$130.25	$130.25	$130.30
Purchase #4	$160.55	3.824%	$166.6894	$166.69	$166.70	$166.70
Purchase #5	$102.31	11.649%	$114.2281	$114.23	$114.25	$114.20
Purchase #6	$171.25	11.488%	$190.9232	$190.92	$190.90	$190.90
Purchase #7	$158.33	8.531%	$171.8371	$171.84	$171.85	$171.80
7 purchase totals =	$943.83		$1,037.0749	$1,037.08	$1,037.10	$1,037.10