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	$79.59	3.223%	$82.1552	$82.16	$82.15	$82.20
Purchase #2	$108.52	4.118%	$112.9889	$112.99	$113.00	$113.00
Purchase #3	$17.43	11.805%	$19.4876	$19.49	$19.50	$19.50
Purchase #4	$200.34	8.612%	$217.5933	$217.59	$217.60	$217.60
Purchase #5	$53.86	9.855%	$59.1679	$59.17	$59.15	$59.20
Purchase #6	$103.97	6.850%	$111.0919	$111.09	$111.10	$111.10
Purchase #7	$22.73	12.688%	$25.614	$25.61	$25.60	$25.60
7 purchase totals =	$586.44		$628.0988	$628.10	$628.10	$628.20