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	$220.84	5.798%	$233.6443	$233.64	$233.65	$233.60
Purchase #2	$76.33	12.482%	$85.8575	$85.86	$85.85	$85.90
Purchase #3	$70.77	10.758%	$78.3834	$78.38	$78.40	$78.40
Purchase #4	$173.25	5.765%	$183.2379	$183.24	$183.25	$183.20
Purchase #5	$107.44	4.544%	$112.3221	$112.32	$112.30	$112.30
Purchase #6	$224.69	7.491%	$241.5215	$241.52	$241.50	$241.50
Purchase #7	$79.89	3.773%	$82.9042	$82.90	$82.90	$82.90
7 purchase totals =	$953.21		$1,017.8709	$1,017.86	$1,017.85	$1,017.80