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	$107.64	5.367%	$113.417	$113.42	$113.40	$113.40
Purchase #2	$18.66	13.374%	$21.1556	$21.16	$21.15	$21.20
Purchase #3	$111.89	7.812%	$120.6308	$120.63	$120.65	$120.60
Purchase #4	$56.69	4.377%	$59.1713	$59.17	$59.15	$59.20
Purchase #5	$52.67	8.387%	$57.0874	$57.09	$57.10	$57.10
Purchase #6	$208.83	6.704%	$222.83	$222.83	$222.85	$222.80
Purchase #7	$162.98	13.218%	$184.5227	$184.52	$184.50	$184.50
7 purchase totals =	$719.36		$778.8148	$778.82	$778.80	$778.80