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	$29.81	4.278%	$31.0853	$31.09	$31.10	$31.10
Purchase #2	$162.36	11.178%	$180.5086	$180.51	$180.50	$180.50
Purchase #3	$113.57	4.417%	$118.5864	$118.59	$118.60	$118.60
Purchase #4	$40.36	9.520%	$44.2023	$44.20	$44.20	$44.20
Purchase #5	$162.98	9.749%	$178.8689	$178.87	$178.85	$178.90
Purchase #6	$43.72	6.377%	$46.508	$46.51	$46.50	$46.50
Purchase #7	$49.32	5.731%	$52.1465	$52.15	$52.15	$52.10
7 purchase totals =	$602.12		$651.9060	$651.92	$651.90	$651.90