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	$81.50	9.341%	$89.1129	$89.11	$89.10	$89.10
Purchase #2	$19.86	10.503%	$21.9459	$21.95	$21.95	$21.90
Purchase #3	$48.55	5.513%	$51.2266	$51.23	$51.25	$51.20
Purchase #4	$139.64	10.567%	$154.3958	$154.40	$154.40	$154.40
Purchase #5	$103.67	3.692%	$107.4975	$107.50	$107.50	$107.50
Purchase #6	$205.56	4.621%	$215.0589	$215.06	$215.05	$215.10
Purchase #7	$28.90	3.314%	$29.8577	$29.86	$29.85	$29.90
7 purchase totals =	$627.68		$669.0953	$669.11	$669.10	$669.10